\r\n \r\n \r\n \r\n \r\n

\r\n\r\n\r\n\r\n\r\n\r\n\r\n\r\n' If you see above, in junk of HTLM, there is text like 'Terme \xc4\x8cate\xc5\xbe' (original is 'Terme ?ate?'). Now, I want to convert code like '\xc4\x8c' or '\xc5\xbe' to unaccented chars so that 'Terme \xc4\x8cate\xc5\xbe' become 'Terme Catez'. Is there any way convert from whole HTML. Thanks in advance. -------------- next part -------------- An HTML attachment was scrubbed... URL: From __peter__ at web.de Tue Jun 8 09:59:31 2010 From: __peter__ at web.de (Peter Otten) Date: Tue, 08 Jun 2010 09:59:31 +0200 Subject: [Tutor] accented characters to unaccented References: Message-ID: KB SU wrote: > Hi, > > I have open url and read like following: > > $import urllib > $txt = urllib.urlopen("http://www.terme-catez.si").read() > $txt > If you see above, in junk of HTLM, there is text like 'Terme > \xc4\x8cate\xc5\xbe' (original is 'Terme ?ate?'). Now, I want to convert > code like '\xc4\x8c' or '\xc5\xbe' to unaccented chars so that 'Terme > \xc4\x8cate\xc5\xbe' become 'Terme Catez'. Is there any way convert from > whole HTML. First convert to unicode with txt = txt.decode("utf-8") and then follow http://effbot.org/zone/unicode-convert.htm Peter From steve at pearwood.info Tue Jun 8 12:07:28 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Tue, 8 Jun 2010 20:07:28 +1000 Subject: [Tutor] no. of references In-Reply-To: <20100608060815.GA23201@scriptkitchen.com> References: <20100608060815.GA23201@scriptkitchen.com> Message-ID: <201006082007.29671.steve@pearwood.info> On Tue, 8 Jun 2010 04:08:15 pm Payal wrote: > Hi, > If I have a list (or a dict), is there any way of knowing how many > other variables are referencing the same object? Sort of. The question is simple, but the answer isn't. It depends what you mean by "variables", and it requires a good understanding of Python's programming model. Python doesn't have "variables" like C or Pascal, it has names and objects. Objects can be bound to no names at all: len([1,2,4]) or to a single name: x = [1,2,4] len(x) or to multiple names: x = y = z = [1,2,4] w = y len(w) Objects can also be referenced by other objects, which in turn could have zero, one or more names. Consider this example: >>> a = [1,2,4] >>> b = a >>> c = {None: ('xyz', b)} >>> class K: ... pass ... >>> d = K() >>> d.attr = [c] Given your question, how many "variables" refer to the list [1,2,4]?, what answer would you expect? Depending on how I count them, I get either 4, 5 or 6: 4: "variables" (names) a, b, c and d 5: the dict globals() has two references to the list, using keys 'a' and 'b'; the tuple ('xyz', b); the dict with key None and value the above tuple; the list [c]; the instance d has a dict __dict__ with key 'attr' 6: same as five, but counting globals() twice Interestingly, Python has a standard tool for tracking referrers, the gc (garbage collector) module, and it disagrees with all of those counts: >>> import gc >>> len(gc.get_referrers(a)) 2 >>> print gc.get_referrers(a) [('xyz', [1, 2, 4]), {'a': [1, 2, 4], 'c': {None: ('xyz', [1, 2, 4])}, 'b': [1, 2, 4], 'd': <__main__.C instance at 0xb7f6008c>, 'gc': , '__builtins__': , 'C': , '__name__': '__main__', '__doc__': None}] So gc says two objects *directly* refer to the list: the tuple, and globals(). But of course there are multiple *indirect* references to the list as well. So the answer you get depends on the way you ask it. -- Steven D'Aprano From davea at ieee.org Tue Jun 8 14:48:48 2010 From: davea at ieee.org (Dave Angel) Date: Tue, 08 Jun 2010 08:48:48 -0400 Subject: [Tutor] no. of references In-Reply-To: <20100608060815.GA23201@scriptkitchen.com> References: <20100608060815.GA23201@scriptkitchen.com> Message-ID: <4C0E3C30.2080405@ieee.org> Payal wrote: > Hi, > If I have a list (or a dict), is there any way of knowing how many other > variables are referencing the same object? > > With warm regards, > -Payal > Depends on what you mean by variables. Try sys.getrefcount(mylist) Naturally, the count will be one higher than you expect. And you should only use this for debugging purposes. DaveA From hugo.yoshi at gmail.com Tue Jun 8 15:03:19 2010 From: hugo.yoshi at gmail.com (Hugo Arts) Date: Tue, 8 Jun 2010 15:03:19 +0200 Subject: [Tutor] no. of references In-Reply-To: <20100608060815.GA23201@scriptkitchen.com> References: <20100608060815.GA23201@scriptkitchen.com> Message-ID: <3718990424089414980@unknownmsgid> On 8 jun 2010, at 08:08, Payal wrote: > Hi, > If I have a list (or a dict), is there any way of knowing how many > other > variables are referencing the same object? > In short, not in any compatible way. If you have a bounded list of names, you can check them with the is operator. But the question "are there any names anywhere in my program that refer to this object?" is generally not answerable. The more relevant question is: why would you want to know this? Hugo From payal-python at scriptkitchen.com Tue Jun 8 16:25:13 2010 From: payal-python at scriptkitchen.com (Payal) Date: Tue, 8 Jun 2010 07:25:13 -0700 Subject: [Tutor] no. of references In-Reply-To: <201006082007.29671.steve@pearwood.info> References: <20100608060815.GA23201@scriptkitchen.com> <201006082007.29671.steve@pearwood.info> Message-ID: <20100608142513.GA28368@scriptkitchen.com> Hi all, Excuse for TOFU. Thanks a lot Steven, Dave and Hugo. Steven the explanation was really great. Thanks a lot for it. Hugo, I was just curious, have no real need. Thanks. With warm regards, -Payal -- On Tue, Jun 08, 2010 at 08:07:28PM +1000, Steven D'Aprano wrote: > On Tue, 8 Jun 2010 04:08:15 pm Payal wrote: > > Hi, > > If I have a list (or a dict), is there any way of knowing how many > > other variables are referencing the same object? > > Sort of. The question is simple, but the answer isn't. It depends what > you mean by "variables", and it requires a good understanding of > Python's programming model. > > Python doesn't have "variables" like C or Pascal, it has names and > objects. Objects can be bound to no names at all: > > len([1,2,4]) > > or to a single name: > > x = [1,2,4] > len(x) > > or to multiple names: > > x = y = z = [1,2,4] > w = y > len(w) > > > Objects can also be referenced by other objects, which in turn could > have zero, one or more names. Consider this example: > > >>> a = [1,2,4] > >>> b = a > >>> c = {None: ('xyz', b)} > >>> class K: > ... pass > ... > >>> d = K() > >>> d.attr = [c] > > > Given your question, how many "variables" refer to the list [1,2,4]?, > what answer would you expect? Depending on how I count them, I get > either 4, 5 or 6: > > 4: > "variables" (names) a, b, c and d > > 5: > the dict globals() has two references to the list, using keys 'a' > and 'b'; > the tuple ('xyz', b); > the dict with key None and value the above tuple; > the list [c]; > the instance d has a dict __dict__ with key 'attr' > > 6: > same as five, but counting globals() twice > > > Interestingly, Python has a standard tool for tracking referrers, the gc > (garbage collector) module, and it disagrees with all of those counts: > > >>> import gc > >>> len(gc.get_referrers(a)) > 2 > >>> print gc.get_referrers(a) > [('xyz', [1, 2, 4]), {'a': [1, 2, 4], 'c': {None: ('xyz', [1, 2, > 4])}, 'b': [1, 2, 4], 'd': <__main__.C instance at 0xb7f6008c>, 'gc': > , '__builtins__': (built-in)>, 'C': 0xb7d0602c>, '__name__': '__main__', '__doc__': None}] > > So gc says two objects *directly* refer to the list: the tuple, and > globals(). But of course there are multiple *indirect* references to > the list as well. So the answer you get depends on the way you ask it. > > > -- > Steven D'Aprano > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor From jf_byrnes at comcast.net Tue Jun 8 18:38:28 2010 From: jf_byrnes at comcast.net (Jim Byrnes) Date: Tue, 08 Jun 2010 11:38:28 -0500 Subject: [Tutor] Tkinter - master attribute Message-ID: <4C0E7204.6080908@comcast.net> When reading code examples I see things like theframe.master.title('spam) or def __init__(self, master): frame = Frame(master) When I encounter these I tend to get bogged down trying to decide if "master" has special meaning or is just a name the author has chosen. For example is it similar to Buttton(text='spam) where text in this case has special meaning. I've goolged and found references to "widgets master attributes" but nothing to really explain it. Could someone point me to a good reference so that I could better understand it use. Thanks, Jim From steve at pearwood.info Tue Jun 8 18:52:08 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Wed, 9 Jun 2010 02:52:08 +1000 Subject: [Tutor] Tkinter - master attribute In-Reply-To: <4C0E7204.6080908@comcast.net> References: <4C0E7204.6080908@comcast.net> Message-ID: <201006090252.09077.steve@pearwood.info> On Wed, 9 Jun 2010 02:38:28 am Jim Byrnes wrote: > When reading code examples I see things like > theframe.master.title('spam) or > def __init__(self, master): > frame = Frame(master) > > When I encounter these I tend to get bogged down trying to decide if > "master" has special meaning or is just a name the author has chosen. > For example is it similar to Buttton(text='spam) where text in this > case has special meaning. To understand Tkinter effectively, you have to know it is an interface to the Tk language (hence the name TK INTERface). Googling on "tk master widget" brings me to this: http://www.tkdocs.com/tutorial/concepts.html which includes this: Geometry management in Tk relies on the concept of master and slave widgets. A master is a widget, typically a toplevel window or a frame, which will contain other widgets, which are called slaves. You can think of a geometry manager as taking control of the master widget, and deciding what will be displayed within. I suppose you could say that master and slave widgets could be named parent and child widgets instead. -- Steven D'Aprano From alan.gauld at btinternet.com Wed Jun 9 00:52:34 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Tue, 8 Jun 2010 23:52:34 +0100 Subject: [Tutor] Tkinter - master attribute References: <4C0E7204.6080908@comcast.net> Message-ID: "Jim Byrnes" wrote in > When reading code examples I see things like > theframe.master.title('spam) > def __init__(self, master): > frame = Frame(master) > When I encounter these I tend to get bogged down trying to decide if > "master" has special meaning or is just a name the author has > chosen. In the first case master is an attribute of the frame and as such is defined by the frame definition. In the second case master is just an arbitrary name for a parameter like any other. Because it is being used to correspond to the master attribute of the Framer(as seen in the call to Frame() ) the author has used the name master too. But other common names for the same attribute are parent, root, top, etc > For example is it similar to Buttton(text='spam) where text in this > case has special meaning. In the first example yes, in the second no. Although 'text' is even more special because it is actually defined in the underlying Tk code rather than in Tkinter Python code. > I've goolged and found references to "widgets master attributes" but > nothing to really explain it. Could someone point me to a good > reference so that I could better understand it use. Because Tkinter is a thin wrapper around the underlying Tk tookit many atttributes of widgets are actually defined in the Tk code and simply mirrored by Tkinter. In that sense the widget attributes tend to have fixed names. But in Tkinter code the naming is essentially arbitrary and follows the usual Python naming conventions. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From ibhatm at gmail.com Wed Jun 9 02:44:16 2010 From: ibhatm at gmail.com (Manju) Date: Wed, 9 Jun 2010 10:44:16 +1000 Subject: [Tutor] Extract from file Message-ID: <004001cb076c$e601a140$b204e3c0$@com> Hi, I need help with extracting information from file. I have a file which is a comma delimited text file containing separate line for each booking. Each line is composed of date, room number, course number and course day. I need to extract only the room number which is entered at the prompt and display course number, date and room number. I have so far managed accept the entry from the prompt, to open the file and display all the text Please help. Regards, Manju -------------- next part -------------- An HTML attachment was scrubbed... URL: From memilanuk at gmail.com Wed Jun 9 05:19:32 2010 From: memilanuk at gmail.com (Monte Milanuk) Date: Tue, 08 Jun 2010 20:19:32 -0700 Subject: [Tutor] Extract from file In-Reply-To: <004001cb076c$e601a140$b204e3c0$@com> References: <004001cb076c$e601a140$b204e3c0$@com> Message-ID: On 6/8/10 5:44 PM, Manju wrote: > Hi, > > I need help with extracting information from file. > > I have a file which is a comma delimited text file containing separate > line for each booking. Each line is composed of date, room number, > course number and course day. Course day??? Not sure what you meant by that, on top of the already mentioned 'date'...? > > I need to extract only the room number which is entered at the prompt > and display course number, date and room number. > > I have so far managed accept the entry from the prompt, to open the file > and display all the text > This may be a case of the blind leading the blind, but here goes: Given this data file (comments not included in actual file): # # example.txt # # date, room, course 2010-06-08,123,246 2009-06-08,234,468 2008-06-08,345,680 # # example.py # room = raw_input("Enter the room #: ") file = open("example.txt", "r") for line in file: line = line.strip() line = line.split(',') if line[1] == room: print "Date: " + line[0] print "Room: " + line[1] print "Course: " + line[2] file.close() >>> Enter the room #: 234 Date: 2009-06-08 Room: 234 Course: 468 >>> HTH, Monte From lang at tharin.com Wed Jun 9 06:11:44 2010 From: lang at tharin.com (Lang Hurst) Date: Tue, 08 Jun 2010 21:11:44 -0700 Subject: [Tutor] Regular expression grouping insert thingy Message-ID: <4C0F1480.6010204@tharin.com> This is so trivial (or should be), but I can't figure it out. I'm trying to do what in vim is :s/$[0-9]$x/\1*x/ That is, "find a number followed by an x and put a "*" in between the number and the x" So, if the string is "6443x - 3", I'll get back "6443*x - 3" I won't write down all the things I've tried, but suffice it to say, nothing has done it. I just found myself figuring out how to call sed and realized that this should be a one-liner in python too. Any ideas? I've read a lot of documentation, but I just can't figure it out. Thanks. -- There are no stupid questions, just stupid people. From woodm1979 at gmail.com Wed Jun 9 06:17:59 2010 From: woodm1979 at gmail.com (Matthew Wood) Date: Tue, 8 Jun 2010 22:17:59 -0600 Subject: [Tutor] Regular expression grouping insert thingy In-Reply-To: <4C0F1480.6010204@tharin.com> References: <4C0F1480.6010204@tharin.com> Message-ID: re.sub(r'(\d+)x', r'\1*x', input_text) -- I enjoy haiku but sometimes they don't make sense; refrigerator? On Tue, Jun 8, 2010 at 10:11 PM, Lang Hurst wrote: > This is so trivial (or should be), but I can't figure it out. > > I'm trying to do what in vim is > > :s/$[0-9]$x/\1*x/ > > That is, "find a number followed by an x and put a "*" in between the > number and the x" > > So, if the string is "6443x - 3", I'll get back "6443*x - 3" > > I won't write down all the things I've tried, but suffice it to say, > nothing has done it. I just found myself figuring out how to call sed and > realized that this should be a one-liner in python too. Any ideas? I've > read a lot of documentation, but I just can't figure it out. Thanks. > > -- > There are no stupid questions, just stupid people. > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > -------------- next part -------------- An HTML attachment was scrubbed... URL: From lang at tharin.com Wed Jun 9 06:27:55 2010 From: lang at tharin.com (Lang Hurst) Date: Tue, 08 Jun 2010 21:27:55 -0700 Subject: [Tutor] Regular expression grouping insert thingy In-Reply-To: References: <4C0F1480.6010204@tharin.com> Message-ID: <4C0F184B.5070006@tharin.com> Oh. Crap, I knew it would be something simple, but honestly, I don't think that I would have gotten there. Thank you so much. Seriously saved me more grey hair. Matthew Wood wrote: > re.sub(r'(\d+)x', r'\1*x', input_text) > > -- > > I enjoy haiku > but sometimes they don't make sense; > refrigerator? > > > On Tue, Jun 8, 2010 at 10:11 PM, Lang Hurst > wrote: > > This is so trivial (or should be), but I can't figure it out. > > I'm trying to do what in vim is > > :s/$[0-9]$x/\1*x/ > > That is, "find a number followed by an x and put a "*" in between > the number and the x" > > So, if the string is "6443x - 3", I'll get back "6443*x - 3" > > I won't write down all the things I've tried, but suffice it to > say, nothing has done it. I just found myself figuring out how to > call sed and realized that this should be a one-liner in python > too. Any ideas? I've read a lot of documentation, but I just > can't figure it out. Thanks. > > -- > There are no stupid questions, just stupid people. > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > -- There are no stupid questions, just stupid people. From eddie9139 at gmail.com Wed Jun 9 13:52:52 2010 From: eddie9139 at gmail.com (Eddie) Date: Wed, 9 Jun 2010 21:52:52 +1000 Subject: [Tutor] Removing an archived message Message-ID: To an admin of this group: Is it possible to get an archived email on the web of mien from thsi group containing personal info about me removed? Thanks -------------- next part -------------- An HTML attachment was scrubbed... URL: From jjcrump at uw.edu Wed Jun 9 20:40:29 2010 From: jjcrump at uw.edu (jjcrump at uw.edu) Date: Wed, 9 Jun 2010 11:40:29 -0700 (PDT) Subject: [Tutor] treeTraversal, nested return? In-Reply-To: References:

Message-ID: Thanks to Matthew and Denis for trying to enlighten me. Thanks to your clues I've made some progress; however, I can't seem to get the hang of the usual recursion trick of keeping track of the level one is on. It doesn't work, I suppose, because the data structure I'm traversing isn't actually nested, its a flat series of lists of tuples. I did finally get a function to traverse the "tree-like" data coming from the db getRecord() returns a tuple of record-type, record-id, parent-id, and title, thus: ('work', 47302, 47301, 'record title') getImages(id) returns a list of 'image' tuples whose parent-id is id getWorks(id) returns a list of 'work' tuples whose parent-id is id works can be nodes, images can't so: def makeDecendentList(id, result): result.append(getRecord(id)) if getImages(id): for x in getImages(id): result.append(x) if not getWorks(id): return else: for y in getWorks(id): makeDecendentList(y[1],result) return result called with the empty list as the second argument. Well and good. This walks the 'tree' (following the parent-ids) and returns me a list of all the decendents of id. But what I wanted was a nested data structure. In the fashion of an ape given a typewriter and sufficient time, I trial and errored my way to this: def makeNestedLists(id): result = [] result.append(getRecord(id)) result.extend(getImages(id)) if not getWorks(id): return result else: result.extend([makeNestedLists(x[1]) for x in getWorks(id)]) return result To my surprise, this gets me exactly what I wanted, eg: [ ('work', 47301, 47254, 'a title'), ('image', 36871, 47301, 'a title'), ('image', 36872, 47301, 'a title'), [ ('work', 47302, 47301, 'a title'), ('image', 10706, 47302, 'a title'), ('image', 10725, 47302, 'a title') ] ] To my surprise, I say, because it looks like it shouldn't work at all with the result being set to the empty list with each recursion; moreover, if I spell out the loop in the list comp like this: def makeNestedLists(id): result = [] result.append(getRecord(id)) result.extend(getImages(id)) if not getWorks(id): return result else: for x in getWorks(id): result.extend(makeNestedLists(x[1])) return result I once again get a flat list of all the decendents of id. I know it's sad, but can any wise tutor explain to me what's going on in the code that I myself wrote? Thanks, Jon From woodm1979 at gmail.com Wed Jun 9 22:31:25 2010 From: woodm1979 at gmail.com (Matthew Wood) Date: Wed, 9 Jun 2010 14:31:25 -0600 Subject: [Tutor] Fwd: treeTraversal, nested return? In-Reply-To: References:

Message-ID: Gah, hit the reply button instead of reply-all. :-( -- I enjoy haiku but sometimes they don't make sense; refrigerator? ---------- Forwarded message ---------- From: Matthew Wood Date: Wed, Jun 9, 2010 at 2:30 PM Subject: Re: [Tutor] treeTraversal, nested return? To: jjcrump at uw.edu Well, I've taken a look at your code. In your last example, the appending last line here: > else: > for x in getWorks(id): > result.extend(makeNestedLists(x[1])) uses, a list.extend call. If you switch that to append, you SHOULD see the result you're looking for. ...at least as best I can guess without replicating the code and having some good test cases. Here's some of your other questions: >To my surprise, I say, because it looks like it shouldn't work at all >with the result being set to the empty list with each recursion; Each time you call the function 'makeNestedLists' a new copy of all the local variables is created. Thus, you aren't blanking the 'result' list each time; instead you're creating a new list each time. Then, when you return the list, you then shove it into the parent-function-instance list. Just take care to understand the difference between: [1, 2, 3].append([4, 5, 6]) -> [1, 2, 3, [4, 5, 6]] [1, 2, 3].extend([4, 5, 6]) -> [1, 2, 3, 4, 5, 6] Your list comprehension example above adds an extra list wrapper around things, which is why the extend worked. -- I enjoy haiku but sometimes they don't make sense; refrigerator? On Wed, Jun 9, 2010 at 12:40 PM, wrote: > Thanks to Matthew and Denis for trying to enlighten me. Thanks to your > clues I've made some progress; however, I can't seem to get the hang of the > usual recursion trick of keeping track of the level one is on. It doesn't > work, I suppose, because the data structure I'm traversing isn't actually > nested, its a flat series of lists of tuples. > > I did finally get a function to traverse the "tree-like" data coming from > the db > > getRecord() returns a tuple of record-type, record-id, parent-id, and > title, thus: > ('work', 47302, 47301, 'record title') > > getImages(id) returns a list of 'image' tuples whose parent-id is id > getWorks(id) returns a list of 'work' tuples whose parent-id is id > > works can be nodes, images can't > > so: > > def makeDecendentList(id, result): > result.append(getRecord(id)) > if getImages(id): > for x in getImages(id): > result.append(x) > if not getWorks(id): > return > else: > for y in getWorks(id): > makeDecendentList(y[1],result) > return result > > called with the empty list as the second argument. > > Well and good. This walks the 'tree' (following the parent-ids) and returns > me a list of all the decendents of id. But what I wanted was a nested data > structure. > > In the fashion of an ape given a typewriter and sufficient time, I trial > and errored my way to this: > > def makeNestedLists(id): > result = [] > result.append(getRecord(id)) > result.extend(getImages(id)) > if not getWorks(id): > return result > else: > result.extend([makeNestedLists(x[1]) for x in getWorks(id)]) > return result > > To my surprise, this gets me exactly what I wanted, eg: > > [ ('work', 47301, 47254, 'a title'), > ('image', 36871, 47301, 'a title'), > ('image', 36872, 47301, 'a title'), > [ ('work', 47302, 47301, 'a title'), > ('image', 10706, 47302, 'a title'), > ('image', 10725, 47302, 'a title') > ] > ] > > To my surprise, I say, because it looks like it shouldn't work at all with > the result being set to the empty list with each recursion; moreover, if I > spell out the loop in the list comp like this: > > def makeNestedLists(id): > result = [] > result.append(getRecord(id)) > result.extend(getImages(id)) > if not getWorks(id): > return result > else: > for x in getWorks(id): > result.extend(makeNestedLists(x[1])) > return result > > I once again get a flat list of all the decendents of id. > > I know it's sad, but can any wise tutor explain to me what's going on in > the code that I myself wrote? > > Thanks, > Jon > -------------- next part -------------- An HTML attachment was scrubbed... URL: From zubin.mithra at gmail.com Wed Jun 9 11:06:55 2010 From: zubin.mithra at gmail.com (Zubin Mithra) Date: Wed, 9 Jun 2010 14:36:55 +0530 Subject: [Tutor] 2to3 conversion Message-ID: Hey everyone, I was running 2to3 on a particular file and I got the following traceback( http://paste.pocoo.org/show/223468/). The file which I was attempting to convert can be viewed here( http://paste.pocoo.org/show/223469/). Any pointers on what needs to be done? Thanks in advance, Zubin -------------- next part -------------- An HTML attachment was scrubbed... URL: From dkuhlman at rexx.com Wed Jun 9 23:37:34 2010 From: dkuhlman at rexx.com (Dave Kuhlman) Date: Wed, 9 Jun 2010 14:37:34 -0700 Subject: [Tutor] Extract from file In-Reply-To: References: <004001cb076c$e601a140$b204e3c0$@com> Message-ID: <20100609213734.GA24324@cutter.rexx.com> On Tue, Jun 08, 2010 at 08:19:32PM -0700, Monte Milanuk wrote: > > On 6/8/10 5:44 PM, Manju wrote: > >Hi, > > > >I need help with extracting information from file. > > > >I have a file which is a comma delimited text file containing separate > >line for each booking. Each line is composed of date, room number, > >course number and course day. > > Course day??? Not sure what you meant by that, on top of the already > mentioned 'date'...? > > > > >I need to extract only the room number which is entered at the prompt > >and display course number, date and room number. > > > >I have so far managed accept the entry from the prompt, to open the file > >and display all the text > > > Monte gave you a good suggestion *if* you are sure that there is no quoting and, especially, if you are sure that there are no commas inside of quotes in your input data. However, it seems that you are dealing with a CSV (comma separated values) file. Python has a module for that. See: http://docs.python.org/library/csv.html That module might help you write safer code. -- Dave Kuhlman http://www.rexx.com/~dkuhlman From alan.gauld at btinternet.com Thu Jun 10 00:34:12 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Wed, 9 Jun 2010 23:34:12 +0100 Subject: [Tutor] Removing an archived message References: Message-ID: I tried to send a reply to you directly but my mail server errors on your gmail account. Can you please reply to me directly (preferably from another account!) and I'll see what can be done. Alan G. List Moderator "Eddie" wrote in message news:AANLkTilszAzlhRymMaUI3P1QjuzvufCYO085RBIP6Hgp at mail.gmail.com... > To an admin of this group: Is it possible to get an archived email > on the > web of mien from thsi group containing personal info about me > removed? > > Thanks > -------------------------------------------------------------------------------- > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > From vceder at canterburyschool.org Thu Jun 10 01:54:28 2010 From: vceder at canterburyschool.org (Vern Ceder) Date: Wed, 09 Jun 2010 19:54:28 -0400 Subject: [Tutor] 2to3 conversion In-Reply-To: References: Message-ID: <4C1029B4.6070505@canterburyschool.org> Zubin Mithra wrote: > Hey everyone, > > I was running 2to3 on a particular file and I got the following > traceback(http://paste.pocoo.org/show/223468/). > > The file which I was attempting to convert can be viewed > here(http://paste.pocoo.org/show/223469/). > > Any pointers on what needs to be done? The traceback indicates that the utf-8 codec doesn't know how to decode the values at bytes 232-234, yet when I saved the file just now, 2to3 ran without giving that error. In fact it only flagged the exception handling as needing mofications. I wonder if the version served by the pastebin is *exactly* the same as the one you are using on your machine? Cheers, Vern > > Thanks in advance, > Zubin > > > ------------------------------------------------------------------------ > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor -- This time for sure! -Bullwinkle J. Moose ----------------------------- Vern Ceder, Director of Technology Canterbury School, 3210 Smith Road, Ft Wayne, IN 46804 vceder at canterburyschool.org; 260-436-0746; FAX: 260-436-5137 The Quick Python Book, 2nd Ed - http://bit.ly/bRsWDW From memilanuk at gmail.com Thu Jun 10 04:02:21 2010 From: memilanuk at gmail.com (Monte Milanuk) Date: Thu, 10 Jun 2010 02:02:21 +0000 (UTC) Subject: [Tutor] Extract from file References: <004001cb076c$e601a140$b204e3c0$@com> <20100609213734.GA24324@cutter.rexx.com> Message-ID: Dave Kuhlman rexx.com> writes: > > Monte gave you a good suggestion *if* you are sure that there is no > quoting and, especially, if you are sure that there are no commas > inside of quotes in your input data. > > However, it seems that you are dealing with a CSV (comma separated > values) file. Python has a module for that. See: > > http://docs.python.org/library/csv.html > > That module might help you write safer code. > Well, like I said... 'blind leading the blind'. I was piecing it together from what I've been exposed to. I had a feeling there was a csv function out there but not having any experience with it I stuck with what I had seen. Reading up on the csv file reading function, it does appear to be a *much* better solution for reading the file and processing the contents! Monte From prasadaraon50 at gmail.com Thu Jun 10 17:14:56 2010 From: prasadaraon50 at gmail.com (prasad rao) Date: Thu, 10 Jun 2010 20:44:56 +0530 Subject: [Tutor] Doubts galore. Message-ID: Hi def cript(doc=None,data =None): if doc==None and data==None:doc=sys.agv1 elif doc: data=open(doc,'r').read() data_c= binascii.hexlify(data) else:data_c= binascii.hexlify(data) if doc: q=tempfile.TemporaryFile() q.write(data_c) os.rename(q,doc) return return data_c cript(doc='./language.txt') Traceback (most recent call last): File "", line 1, in File "", line 10, in cript TypeError: coercing to Unicode: need string or buffer, file found 1)Why I got the above error message with the above function?How to correct it? 2)Is it reasonable to have 2 if blocks in a function as above? 3)Dose the tempfile create a fileobject on harddisk or in memory(Dose it save my file as I expect it to do) Please someone enlighten me. Prasad From steve at alchemy.com Thu Jun 10 17:26:28 2010 From: steve at alchemy.com (Steve Willoughby) Date: Thu, 10 Jun 2010 08:26:28 -0700 Subject: [Tutor] Doubts galore. In-Reply-To: References: Message-ID: <20100610152628.GA1715@dragon.alchemy.com> On Thu, Jun 10, 2010 at 08:44:56PM +0530, prasad rao wrote: > Hi > > def cript(doc=None,data =None): > if doc==None and data==None:doc=sys.agv1 Never NEVER compare for equality with None. What you want is: if doc is None and data is None: Also, what is "sys.agv1"? Did you mean sys.argv[1]? > elif doc: > data=open(doc,'r').read() > data_c= binascii.hexlify(data) > else:data_c= binascii.hexlify(data) > if doc: > q=tempfile.TemporaryFile() > q.write(data_c) > os.rename(q,doc) > return > return data_c It would probably be cleaner to use one-line conditional statements (sparingly) where they make sense on their own, but not to mix multi-line and single line styles in the same if-else structure. I'm not sure the logical flow through there does what you think it does, though. > cript(doc='./language.txt') > Traceback (most recent call last): > File "", line 1, in > File "", line 10, in cript > TypeError: coercing to Unicode: need string or buffer, file found > Is this the actual code or did you retype it? It has some typos which makes me wonder. If you copy/paste the actual code that can remove any confusion introduced by simple typing mistakes, so we are sure we're all looking at the same thing here. > 1)Why I got the above error message with the above function?How to correct it? The binascii.hexlify() function converts a binary data string into hexadecimal digits. You didn't give it a data string to work from, you gave it an open file object. You'll need to actually read the data from the file and give that to the function. > 2)Is it reasonable to have 2 if blocks in a function as above? Sure > 3)Dose the tempfile create a fileobject on harddisk or in memory(Dose it save my > file as I expect it to do) It creates a TEMPORARY file. That means you can expect it to exist on disk until you close it, and then if at all possible, it will automatically be destroyed for you. Hence "temporary". Depending on your platform, while there will be a physical disk file, it might not even show up in a directory or be openable by other applications. If you want a file to not be temporary, use open() to create it. > > Please someone enlighten me. > > Prasad > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor -- Steve Willoughby | Using billion-dollar satellites steve at alchemy.com | to hunt for Tupperware. From lie.1296 at gmail.com Thu Jun 10 17:41:11 2010 From: lie.1296 at gmail.com (Lie Ryan) Date: Fri, 11 Jun 2010 01:41:11 +1000 Subject: [Tutor] Doubts galore. In-Reply-To: References: Message-ID: On 06/11/10 01:14, prasad rao wrote: > Hi > > def cript(doc=None,data =None): > if doc==None and data==None:doc=sys.agv1 > elif doc: > data=open(doc,'r').read() > data_c= binascii.hexlify(data) > else:data_c= binascii.hexlify(data) > if doc: > q=tempfile.TemporaryFile() > q.write(data_c) > os.rename(q,doc) > return > return data_c > > > cript(doc='./language.txt') > Traceback (most recent call last): > File "", line 1, in > File "", line 10, in cript > TypeError: coercing to Unicode: need string or buffer, file found > > 1)Why I got the above error message with the above function?How to correct it? The error message points out here: # line 10 os.rename(q,doc) ^^^ scanning a few lines earlier, we saw: q=tempfile.TemporaryFile() os.rename() doesn't rename a file object; os.rename() takes two string arguments. > 2)Is it reasonable to have 2 if blocks in a function as above? This is where boolean algebra can help. An elif-block will only be run when all the if-elif blocks before it evaluates to false. IOW, your code is equivalent to this: if doc==None and data==None: doc=sys.agv1 if not (doc==None and data==None) and doc: data=open(doc,'r').read() data_c= binascii.hexlify(data) except that "doc==None and data==None" is only evaluated once. So, using boolean algebra (assuming a reasonable definition of == and !=): not (doc==None and data==None) and doc (doc!=None or data!=None) and doc now depending on the intent of "doc" and "doc != None"; it may be possible to simplify that to only: data != None. Note that this is all assuming a reasonable definition of ==, !=, not, etc and assuming no side effects and assuming that the checks are equally lightweight. > 3)Dose the tempfile create a fileobject on harddisk or in memory(Dose it save my > file as I expect it to do) AFAIK, tempfile creates a file in harddisk, but I've never used tempfile, so don't quote me on that. From prasadaraon50 at gmail.com Thu Jun 10 18:13:34 2010 From: prasadaraon50 at gmail.com (prasad rao) Date: Thu, 10 Jun 2010 21:43:34 +0530 Subject: [Tutor] Doubts galore. In-Reply-To: <20100610152628.GA1715@dragon.alchemy.com> References: <20100610152628.GA1715@dragon.alchemy.com> Message-ID: > Never NEVER compare for equality with None. > > What you want is: > if doc is None and data is None: > > Also, what is "sys.agv1"? Did you mean sys.argv[1]? yes > > elif doc: > > data=open(doc,'r').read() > > data_c= binascii.hexlify(data) > > else:data_c= binascii.hexlify(data) > > if doc: > > q=tempfile.TemporaryFile() > > q.write(data_c) > > os.rename(q,doc) > > return > > return data_c > It would probably be cleaner to use one-line > conditional statements (sparingly) where they make > sense on their own, but not to mix multi-line and > single line styles in the same if-else structure. I am a newbie.I couldn't understand that comment. > I'm not sure the logical flow through there > does what you think it does, though. > > cript(doc='./language.txt') > > Traceback (most recent call last): > > File "", line 1, in > > File "", line 10, in cript > > TypeError: coercing to Unicode: need string or buffer, file found > Is this the actual code or did you retype it? I just copied from .py file and pasted. > It has some typos which makes me wonder. If you copy/paste > the actual code that can remove any confusion introduced > by simple typing mistakes, so we are sure we're all looking > at the same thing here. > > > > 1)Why I got the above error message with the above function?How to correct it? > > > The binascii.hexlify() function converts a binary data string into > hexadecimal digits. You didn't give it a data string to work from, > you gave it an open file object. You'll need to actually read the > data from the file and give that to the function. > > > > 2)Is it reasonable to have 2 if blocks in a function as above? > > > Sure > > > > 3)Dose the tempfile create a fileobject on harddisk or in memory(Dose it save my > > file as I expect it to do) > > > It creates a TEMPORARY file. That means you can expect it to > exist on disk until you close it, and then if at all possible, > it will automatically be destroyed for you. Hence "temporary". > Depending on your platform, while there will be a physical disk > file, it might not even show up in a directory or be openable by > other applications. > > If you want a file to not be temporary, use open() to create it. > Steve Willoughby | Using billion-dollar satellites > steve at alchemy.com | to hunt for Tupperware. Thanks for the reply..Now I will try to correct my code. From steve at alchemy.com Thu Jun 10 19:11:10 2010 From: steve at alchemy.com (Steve Willoughby) Date: Thu, 10 Jun 2010 10:11:10 -0700 Subject: [Tutor] Doubts galore. In-Reply-To: References: <20100610152628.GA1715@dragon.alchemy.com> Message-ID: <20100610171110.GB1715@dragon.alchemy.com> On Thu, Jun 10, 2010 at 09:43:34PM +0530, prasad rao wrote: > > It would probably be cleaner to use one-line > > conditional statements (sparingly) where they make > > sense on their own, but not to mix multi-line and > > single line styles in the same if-else structure. > > I am a newbie.I couldn't understand that comment. So occasionally it's cleaner and clearer to put the condition and statement on one line like if x>0: print x But often you need more than one line, so you make a block structure: if x>0: do_stuff() do_more_stuff() If you have multiple blocks in an if-elif-elif-...-else structure, don't go back and forth between one-line and multi-line blocks, be consistent, so instead of something like if x>0: do_one_thing() elif x<0: do_something_else(-x) something_entirely_different(x**2) elif x==0 and y>0: do_something_else(y) yet_another_function(y**3) else: raise ValueError('values for x and y not in allowed range') you should be consistent and write this as: if x>0: do_one_thing() elif x<0: do_something_else(-x) something_entirely_different(x**2) elif x==0 and y>0: do_something_else(y) yet_another_function(y**3) else: raise ValueError('values for x and y not in allowed range') -- Steve Willoughby | Using billion-dollar satellites steve at alchemy.com | to hunt for Tupperware. From beachkid at insightbb.com Fri Jun 11 15:57:34 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 09:57:34 -0400 Subject: [Tutor] Looking for duplicates within a list Message-ID: <4C1240CE.7050807@insightbb.com> I have been working on this problem for several days and I am not making any progress. I have a group of 18 number, in ascending order, within a list. They ranged from 1 to 39. Some numbers are duplicated as much as three times or as few as none. I started with one list containing the numbers. For example, they are listed as like below: a = [1, 2, 3, 3, 4] I started off with using a loop: for j in range (0, 5): x = a[0] # for example, 1 How would I compare '1' with 2, 3, 3, 4? Do I need another duplicated list such as b = a and compare a[0] with either b[0], b[1], b[2], b[3], b[4]? Or do I compare a[0] with a[1], a[2], a[3], a[4]? In any event, if a number is listed more than once, I would like to know how many times, such as 2 or 3 times. For example, '3' is listed twice within a list. TIA, Ken From mehgcap at gmail.com Fri Jun 11 16:20:20 2010 From: mehgcap at gmail.com (Alex Hall) Date: Fri, 11 Jun 2010 10:20:20 -0400 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <4C1240CE.7050807@insightbb.com> References: <4C1240CE.7050807@insightbb.com> Message-ID: On 6/11/10, Ken G. wrote: > I have been working on this problem for several days and I am not making > any progress. I have a group of 18 number, in ascending order, within a > list. They ranged from 1 to 39. Some numbers are duplicated as much as > three times or as few as none. FYI, Python's "set" data type will let you have a list and never have a repeat. I know that is not your goal now, but if you want to remove duplicates, it seems like a good choice. > > I started with one list containing the numbers. For example, they are > listed as like below: > > a = [1, 2, 3, 3, 4] > > I started off with using a loop: > > for j in range (0, 5): > x = a[0] # for example, 1 > > How would I compare '1' with 2, 3, 3, 4? > > Do I need another duplicated list such as b = a and compare a[0] with > either b[0], b[1], b[2], b[3], b[4]? > > Or do I compare a[0] with a[1], a[2], a[3], a[4]? A couple points here. First, you will want to make life easier by saying range(0, len(a)) so that the loop will work no matter the size of a. Second, for comparing a list to itself, here is a rather inefficient, though simple, way: for i in range(0, len(a)): x=a[i] for j in range(0, len(a)): y=a[j] if(x==y and i!=j): #match since a[i]==a[j] and i and j are not the same index of a > > In any event, if a number is listed more than once, I would like to know > how many times, such as 2 or 3 times. For example, '3' is listed twice > within a list. Do not quote me here, but I think sets may be able to tell you that as well. > > TIA, > > Ken > > > > > > > > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > -- Have a great day, Alex (msg sent from GMail website) mehgcap at gmail.com; http://www.facebook.com/mehgcap From beachkid at insightbb.com Fri Jun 11 16:31:58 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 10:31:58 -0400 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <630560.5642.qm@web95316.mail.in2.yahoo.com> References: <630560.5642.qm@web95316.mail.in2.yahoo.com> Message-ID: <4C1248DE.6090508@insightbb.com> vijay wrote: > Check out this code > l= [1, 2, 3, 3, 4] > d={} > for item in l: > d.setdefaut(item,0) > d[item] +=1 > print d > {1: 1, 2: 1, 3: 2, 4: 1} > > > with regard's > vijay > > Thanks. Very interesting concept. Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: From beachkid at insightbb.com Fri Jun 11 16:40:58 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 10:40:58 -0400 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: References: <4C1240CE.7050807@insightbb.com> Message-ID: <4C124AFA.7030007@insightbb.com> Alex Hall wrote: > On 6/11/10, Ken G. wrote: > >> I have been working on this problem for several days and I am not making >> any progress. I have a group of 18 number, in ascending order, within a >> list. They ranged from 1 to 39. Some numbers are duplicated as much as >> three times or as few as none. >> > FYI, Python's "set" data type will let you have a list and never have > a repeat. I know that is not your goal now, but if you want to remove > duplicates, it seems like a good choice. > >> I started with one list containing the numbers. For example, they are >> listed as like below: >> >> a = [1, 2, 3, 3, 4] >> >> I started off with using a loop: >> >> for j in range (0, 5): >> x = a[0] # for example, 1 >> >> How would I compare '1' with 2, 3, 3, 4? >> >> Do I need another duplicated list such as b = a and compare a[0] with >> either b[0], b[1], b[2], b[3], b[4]? >> >> Or do I compare a[0] with a[1], a[2], a[3], a[4]? >> > A couple points here. First, you will want to make life easier by > saying range(0, len(a)) so that the loop will work no matter the size > of a. > Second, for comparing a list to itself, here is a rather inefficient, > though simple, way: > > for i in range(0, len(a)): > x=a[i] > for j in range(0, len(a)): > y=a[j] > if(x==y and i!=j): #match since a[i]==a[j] and i and j are not the > same index of a > >> In any event, if a number is listed more than once, I would like to know >> how many times, such as 2 or 3 times. For example, '3' is listed twice >> within a list. >> > Do not quote me here, but I think sets may be able to tell you that as well. > >> TIA, >> >> Ken >> Thank you for your contribution. As seen here, I have much to learn. Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: From sander.sweers at gmail.com Fri Jun 11 16:46:25 2010 From: sander.sweers at gmail.com (Sander Sweers) Date: Fri, 11 Jun 2010 16:46:25 +0200 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <4C1240CE.7050807@insightbb.com> References: <4C1240CE.7050807@insightbb.com> Message-ID: On 11 June 2010 15:57, Ken G. wrote: > In any event, if a number is listed more than once, I would like to know how > many times, such as 2 or 3 times. ?For example, '3' is listed twice within a > list. If you do not have top keep the order of the number this will work. >>> a = [1, 2, 3, 3, 4] >>> counted = {} >>> for n in a: if not n in counted: counted[n] = 1 else: counted[n] += 1 >>> counted {1: 1, 2: 1, 3: 2, 4: 1} >>> for x, y in counted.items(): if y > 1: print "Number %s was found %s times" % (x, y) else: print "Number %s was found %s time" % (x, y) Number 1 was found 1 time Number 2 was found 1 time Number 3 was found 2 times Number 4 was found 1 time Greets Sander From ljmamoreira at gmail.com Fri Jun 11 16:49:22 2010 From: ljmamoreira at gmail.com (Jose Amoreira) Date: Fri, 11 Jun 2010 15:49:22 +0100 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <4C1240CE.7050807@insightbb.com> References: <4C1240CE.7050807@insightbb.com> Message-ID: <201006111549.22751.ljmamoreira@gmail.com> On Friday, June 11, 2010 02:57:34 pm Ken G. wrote: > I have been working on this problem for several days and I am not making > any progress. I have a group of 18 number, in ascending order, within a > list. They ranged from 1 to 39. Some numbers are duplicated as much as > three times or as few as none. > > I started with one list containing the numbers. For example, they are > listed as like below: > > a = [1, 2, 3, 3, 4] > > I started off with using a loop: > > for j in range (0, 5): > x = a[0] # for example, 1 > > How would I compare '1' with 2, 3, 3, 4? > > Do I need another duplicated list such as b = a and compare a[0] with > either b[0], b[1], b[2], b[3], b[4]? > > Or do I compare a[0] with a[1], a[2], a[3], a[4]? > > In any event, if a number is listed more than once, I would like to know > how many times, such as 2 or 3 times. For example, '3' is listed twice > within a list. > > TIA, > I would do it with a dictionary: def reps(lst): dict = {} for item in lst: if item in dict: dict[item] += 1 else: dict[item] = 1 return dict This function returns a dictionary with of the number of times each value in the list is repeated. Even shorter using dict.setdefault: def reps(lst): dict={} for item in lst: dict[item] = dict.setdefault(item,0) + 1 return dict For instance, if lst=[1,2,2,2,4,4,5], then reps(lst) returns {1: 1, 2: 3, 4: 2, 5: 1} Using the fact that the list is ordered, one can design a more efficient solution (go through the list; if this item is equal to the previous, then it is repeated, else, it is a new value). But you list is short enough for this direct approach to work. Hope this helps. Cheers, Jose From alan.gauld at btinternet.com Fri Jun 11 16:58:19 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Fri, 11 Jun 2010 15:58:19 +0100 Subject: [Tutor] Looking for duplicates within a list References: <4C1240CE.7050807@insightbb.com> Message-ID: "Ken G." wrote > In any event, if a number is listed more than once, I would like to > know how many times, such as 2 or 3 times. For example, '3' is > listed twice within a list. Have you looked at the count method of lists? Something like: counts = set(( item, mylist.count(item)) for item in mylist if mylist.count(item) > 1) Seems to work... HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From beachkid at insightbb.com Fri Jun 11 17:16:38 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 11:16:38 -0400 Subject: [Tutor] Looking for duplicates within a list [SOLVED] In-Reply-To: References: <4C1240CE.7050807@insightbb.com> Message-ID: <4C125356.5030708@insightbb.com> Sander Sweers wrote: > On 11 June 2010 15:57, Ken G. wrote: > >> In any event, if a number is listed more than once, I would like to know how >> many times, such as 2 or 3 times. For example, '3' is listed twice within a >> list. >> > > If you do not have top keep the order of the number this will work. > > >>>> a = [1, 2, 3, 3, 4] >>>> counted = {} >>>> for n in a: >>>> > if not n in counted: > counted[n] = 1 > else: > counted[n] += 1 > > >>>> counted >>>> > {1: 1, 2: 1, 3: 2, 4: 1} > > >>>> for x, y in counted.items(): >>>> > if y > 1: > print "Number %s was found %s times" % (x, y) > else: > print "Number %s was found %s time" % (x, y) > > Number 1 was found 1 time > Number 2 was found 1 time > Number 3 was found 2 times > Number 4 was found 1 time > > Greets > Sander > That works great! Thanks! Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: From beachkid at insightbb.com Fri Jun 11 17:17:57 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 11:17:57 -0400 Subject: [Tutor] Looking for duplicates within a list [SOLVED] In-Reply-To: <201006111549.22751.ljmamoreira@gmail.com> References: <4C1240CE.7050807@insightbb.com> <201006111549.22751.ljmamoreira@gmail.com> Message-ID: <4C1253A5.7000304@insightbb.com> Jose Amoreira wrote: > On Friday, June 11, 2010 02:57:34 pm Ken G. wrote: > >> I have been working on this problem for several days and I am not making >> any progress. I have a group of 18 number, in ascending order, within a >> list. They ranged from 1 to 39. Some numbers are duplicated as much as >> three times or as few as none. >> >> I started with one list containing the numbers. For example, they are >> listed as like below: >> >> a = [1, 2, 3, 3, 4] >> >> I started off with using a loop: >> >> for j in range (0, 5): >> x = a[0] # for example, 1 >> >> How would I compare '1' with 2, 3, 3, 4? >> >> Do I need another duplicated list such as b = a and compare a[0] with >> either b[0], b[1], b[2], b[3], b[4]? >> >> Or do I compare a[0] with a[1], a[2], a[3], a[4]? >> >> In any event, if a number is listed more than once, I would like to know >> how many times, such as 2 or 3 times. For example, '3' is listed twice >> within a list. >> >> TIA, >> >> > > I would do it with a dictionary: > def reps(lst): > dict = {} > for item in lst: > if item in dict: > dict[item] += 1 > else: > dict[item] = 1 > return dict > > This function returns a dictionary with of the number of times each value in > the list is repeated. Even shorter using dict.setdefault: > > def reps(lst): > dict={} > for item in lst: > dict[item] = dict.setdefault(item,0) + 1 > return dict > > For instance, if lst=[1,2,2,2,4,4,5], then reps(lst) returns > {1: 1, 2: 3, 4: 2, 5: 1} > > Using the fact that the list is ordered, one can design a more efficient > solution (go through the list; if this item is equal to the previous, then it > is repeated, else, it is a new value). But you list is short enough for this > direct approach to work. > Hope this helps. Cheers, > Jose > > Thanks. I will be studying your approach. Thanks all. Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: From beachkid at insightbb.com Fri Jun 11 17:19:17 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 11:19:17 -0400 Subject: [Tutor] Looking for duplicates within a list [SOLVED] In-Reply-To: References: <4C1240CE.7050807@insightbb.com> Message-ID: <4C1253F5.2090300@insightbb.com> Alan Gauld wrote: > > "Ken G." wrote > >> In any event, if a number is listed more than once, I would like to >> know how many times, such as 2 or 3 times. For example, '3' is >> listed twice within a list. > > Have you looked at the count method of lists? > > Something like: > > counts = set(( item, mylist.count(item)) for item in mylist if > mylist.count(item) > 1) > > Seems to work... > > HTH, > > Whee, this is great! I learned a lot today. Back to playing and studying. Ken From davea at ieee.org Fri Jun 11 17:37:31 2010 From: davea at ieee.org (Dave Angel) Date: Fri, 11 Jun 2010 11:37:31 -0400 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <4C1240CE.7050807@insightbb.com> References: <4C1240CE.7050807@insightbb.com> Message-ID: <4C12583B.5050707@ieee.org> Ken G. wrote: > I have been working on this problem for several days and I am not > making any progress. I have a group of 18 number, in ascending order, > within a list. They ranged from 1 to 39. Some numbers are duplicated > as much as three times or as few as none. > > I started with one list containing the numbers. For example, they are > listed as like below: > > a = [1, 2, 3, 3, 4] > > I started off with using a loop: > > for j in range (0, 5): > x = a[0] # for example, 1 > > How would I compare '1' with 2, 3, 3, 4? > Do I need another duplicated list such as b = a and compare a[0] with > either b[0], b[1], b[2], b[3], b[4]? > > Or do I compare a[0] with a[1], a[2], a[3], a[4]? > > In any event, if a number is listed more than once, I would like to > know how many times, such as 2 or 3 times. For example, '3' is listed > twice within a list. > > TIA, > > Ken > I'm a bit surprised nobody has mentioned the obvious solution -- another list of size 40, each of which represents the number of times a particular number has appeared. (Untested) a = [1, 2, 3, 3, 4] counts = [0] * 40 for item in a: counts[item] += 1 Now, if you want to know how many times 3 appears, simply print counts[3] The only downside to this is if the range of possible values is large, or non-numeric. In either of those cases, go back to the default dictionary. DaveA From steve at pearwood.info Fri Jun 11 17:49:54 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Sat, 12 Jun 2010 01:49:54 +1000 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: References: <4C1240CE.7050807@insightbb.com> Message-ID: <201006120149.55173.steve@pearwood.info> On Sat, 12 Jun 2010 12:58:19 am Alan Gauld wrote: > Have you looked at the count method of lists? > > Something like: > > counts = set(( item, mylist.count(item)) for item in mylist if > mylist.count(item) > 1) That's a Shlemiel the Painter algorithm. http://www.joelonsoftware.com/articles/fog0000000319.html > Seems to work... You say that now, but one day you will use it on a list of 100,000 items, and you'll wonder why it takes 45 minutes to finish, and curse Python for being slow. -- Steven D'Aprano From beachkid at insightbb.com Fri Jun 11 18:08:02 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 12:08:02 -0400 Subject: [Tutor] Looking for duplicates within a list [SOLVED] In-Reply-To: <4C12583B.5050707@ieee.org> References: <4C1240CE.7050807@insightbb.com> <4C12583B.5050707@ieee.org> Message-ID: <4C125F62.50706@insightbb.com> Dave Angel wrote: > Ken G. wrote: >> I have been working on this problem for several days and I am not >> making any progress. I have a group of 18 number, in ascending >> order, within a list. They ranged from 1 to 39. Some numbers are >> duplicated as much as three times or as few as none. >> >> I started with one list containing the numbers. For example, they >> are listed as like below: >> >> a = [1, 2, 3, 3, 4] >> >> I started off with using a loop: >> >> for j in range (0, 5): >> x = a[0] # for example, 1 >> >> How would I compare '1' with 2, 3, 3, 4? >> Do I need another duplicated list such as b = a and compare a[0] with >> either b[0], b[1], b[2], b[3], b[4]? >> >> Or do I compare a[0] with a[1], a[2], a[3], a[4]? >> >> In any event, if a number is listed more than once, I would like to >> know how many times, such as 2 or 3 times. For example, '3' is >> listed twice within a list. >> >> TIA, >> >> Ken >> > I'm a bit surprised nobody has mentioned the obvious solution -- > another list of size 40, each of which represents the number of times > a particular number has appeared. > > (Untested) > > > a = [1, 2, 3, 3, 4] > counts = [0] * 40 > for item in a: > counts[item] += 1 > > Now, if you want to know how many times 3 appears, simply > print counts[3] > > The only downside to this is if the range of possible values is large, > or non-numeric. In either of those cases, go back to the default > dictionary. > > DaveA > > > This will be look into. Mucho thanks. Ken From beachkid at insightbb.com Fri Jun 11 18:09:09 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 12:09:09 -0400 Subject: [Tutor] Looking for duplicates within a list [SOLVED] In-Reply-To: <201006120149.55173.steve@pearwood.info> References: <4C1240CE.7050807@insightbb.com> <201006120149.55173.steve@pearwood.info> Message-ID: <4C125FA5.8000403@insightbb.com> Steven D'Aprano wrote: > On Sat, 12 Jun 2010 12:58:19 am Alan Gauld wrote: > > >> Have you looked at the count method of lists? >> >> Something like: >> >> counts = set(( item, mylist.count(item)) for item in mylist if >> mylist.count(item) > 1) >> > > That's a Shlemiel the Painter algorithm. > > http://www.joelonsoftware.com/articles/fog0000000319.html > > > >> Seems to work... >> > > You say that now, but one day you will use it on a list of 100,000 > items, and you'll wonder why it takes 45 minutes to finish, and curse > Python for being slow. > Hee, hee. Will investigate further. Thanks. Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: From hugo.yoshi at gmail.com Fri Jun 11 18:18:52 2010 From: hugo.yoshi at gmail.com (Hugo Arts) Date: Fri, 11 Jun 2010 18:18:52 +0200 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <201006120149.55173.steve@pearwood.info> References: <4C1240CE.7050807@insightbb.com> <201006120149.55173.steve@pearwood.info> Message-ID: <2114901386686547039@unknownmsgid> On 11 jun 2010, at 17:49, Steven D'Aprano wrote: > On Sat, 12 Jun 2010 12:58:19 am Alan Gauld wrote: > >> Have you looked at the count method of lists? >> >> Something like: >> >> counts = set(( item, mylist.count(item)) for item in mylist if >> mylist.count(item) > 1) > > That's a Shlemiel the Painter algorithm. > > http://www.joelonsoftware.com/articles/fog0000000319.html > It is, but it's also very elegant and simple to understand. And it works fine on small inputs. Everything is fast for small n. > >> Seems to work... > > You say that now, but one day you will use it on a list of 100,000 > items, and you'll wonder why it takes 45 minutes to finish, and curse > Python for being slow. > Actually, now that you know it is a shlemiel the painter's algorithm, you won't have to wonder anymore. And you'll just say: "well, this piece of code might need to handle huge lists someday, I'll use a dictionary." I guess what I'm trying to say is: using code that performs bad in situations that won't be encountered anyway is not inherently bad. Otherwise, we'd all still be writing everything in C. The corrolary, of course, is that you should always know what the performance characteristics of your code are, and what kind of data it will handle. Hugo From davidheiserca at gmail.com Fri Jun 11 18:22:55 2010 From: davidheiserca at gmail.com (davidheiserca at gmail.com) Date: Fri, 11 Jun 2010 09:22:55 -0700 Subject: [Tutor] Looking for duplicates within a list [SOLVED] References: <4C1240CE.7050807@insightbb.com> <201006120149.55173.steve@pearwood.info> <4C125FA5.8000403@insightbb.com> Message-ID: How about this? List = [1, 2, 3, 3, 3, 4, 5, 5] for Item in list(set(List)): print Item, List.count(Item) ----- Original Message ----- From: Ken G. To: Steven D'Aprano Cc: tutor at python.org Sent: Friday, June 11, 2010 9:09 AM Subject: Re: [Tutor] Looking for duplicates within a list [SOLVED] Steven D'Aprano wrote: On Sat, 12 Jun 2010 12:58:19 am Alan Gauld wrote: Have you looked at the count method of lists? Something like: counts = set(( item, mylist.count(item)) for item in mylist if mylist.count(item) > 1) That's a Shlemiel the Painter algorithm. http://www.joelonsoftware.com/articles/fog0000000319.html Seems to work... You say that now, but one day you will use it on a list of 100,000 items, and you'll wonder why it takes 45 minutes to finish, and curse Python for being slow. Hee, hee. Will investigate further. Thanks. Ken ------------------------------------------------------------------------------ _______________________________________________ Tutor maillist - Tutor at python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor -------------- next part -------------- An HTML attachment was scrubbed... URL: From steve at pearwood.info Fri Jun 11 19:28:30 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Sat, 12 Jun 2010 03:28:30 +1000 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <2114901386686547039@unknownmsgid> References: <4C1240CE.7050807@insightbb.com> <201006120149.55173.steve@pearwood.info> <2114901386686547039@unknownmsgid> Message-ID: <201006120328.31344.steve@pearwood.info> On Sat, 12 Jun 2010 02:18:52 am Hugo Arts wrote: > On 11 jun 2010, at 17:49, Steven D'Aprano wrote: > > On Sat, 12 Jun 2010 12:58:19 am Alan Gauld wrote: > >> Have you looked at the count method of lists? > >> > >> Something like: > >> > >> counts = set(( item, mylist.count(item)) for item in mylist if > >> mylist.count(item) > 1) > > > > That's a Shlemiel the Painter algorithm. > > > > http://www.joelonsoftware.com/articles/fog0000000319.html > > It is, but it's also very elegant and simple to understand. Your idea of elegant and simple is not the same as mine. To me, I see unnecessary work and unneeded complexity. A generator expression for a beginner having trouble with the basics? Calling mylist.count(item) *twice* for every item?! How is that possibly elegant? > And it > works fine on small inputs. Everything is fast for small n. [pedantic] Not everything. Some things are inherently slow, for example: http://en.wikipedia.org/wiki/Busy_beaver A five-state Busy Beaver machine takes 47,176,870 steps to return, and a six-state Busy Beaver takes 10**21132 steps to return. A slightly less extreme example is Ackermann's Function: http://en.wikipedia.org/wiki/Ackermann's_function where (for example) A(4,2) has over 19,000 digits. Calculating the number of recursive steps needed to calculate that value is left as an exercise. [/pedantic] These are extreme examples, but the point is that there are tasks which are hard even for small N. "Find N needles in a haystack" remains hard even for N=1. (And before you suggest using a magnet, it's a *plastic* needle.) [...] > I guess what I'm trying to say is: using code that performs bad in > situations that won't be encountered anyway is not inherently bad. The problem is that situations that won't be encountered often *are* encountered, long after the coder who introduced the poorly-performing algorithm has moved on. Here's a real-life example, from Python itself: last September, on the Python-Dev mailing list, Chris Withers reported a problem downloading a file using Python's httplib module. For a file that took wget or Internet Explorer approximately 2 seconds to download, it took Python up to thirty MINUTES -- that's nearly a thousand times slower. Eventually Chris, with the help of others on the list, debugged the problem down to a Shlemiel algorithm in the httplib code. Somebody found a comment in the _read_chunked method that said: ? # XXX This accumulates chunks by repeated string concatenation, ? # which is not efficient as the number or size of chunks gets big. So somebody used an algorithm which they KNEW was inefficient and slow, it had been there for years, affecting who knows how many people, until eventually somebody was annoyed sufficiently to do something about it. And the sad thing is that avoiding repeated string concatenation is easy and there was no need for it in the first place. > Otherwise, we'd all still be writing everything in C. You've missed the point. It's not the language, you can write poorly performing code in any language, and an O(N) algorithm in a slow language will probably out-perform an O(N**2) or O(2**N) algorithm in a fast language. -- Steven D'Aprano From steve at pearwood.info Fri Jun 11 19:37:05 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Sat, 12 Jun 2010 03:37:05 +1000 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <4C1240CE.7050807@insightbb.com> References: <4C1240CE.7050807@insightbb.com> Message-ID: <201006120337.05963.steve@pearwood.info> On Fri, 11 Jun 2010 11:57:34 pm Ken G. wrote: > I have been working on this problem for several days and I am not > making any progress. I have a group of 18 number, in ascending > order, within a list. They ranged from 1 to 39. Some numbers are > duplicated as much as three times or as few as none. To find out how many times each number is in the list: counts = {} for i in mylist: # Don't do the work if you've already done it. if i not in counts: counts[i] = mylist.count(i) Can we do better? For very small lists, probably not, because the count() method is implemented in fast C, and anything we write will be in slow-ish Python. But for larger lists, count() is wasteful, because every time you call it, it walks the entire length of the string from start to finish. Since we know the list is sorted, that's a rubbish strategy. Let's write a quick helper function: # Untested def count_equals(alist, start): """Count the number of consecutive items of alist equal to the item at start. Returns the count and the next place to start.""" item = alist[start] count = 1 for i in xrange(start+1, len(alist)): x = alist[i] if x == item: count += 1 else: return (count, i) return (count, len(alist)) Now, with this we can avoid wastefully starting from the beginning of the list each time. (But remember, this will only be worthwhile for sufficiently large lists. My guess, and this is only a guess, is that it won't be worthwhile for lists smaller than perhaps 1,000 items.) counts = {} i = 0 while i < len(mylist): count, i = count_equals(mylist, i) counts[i] = count > I started with one list containing the numbers. For example, they > are listed as like below: > > a = [1, 2, 3, 3, 4] > > I started off with using a loop: > > for j in range (0, 5): > x = a[0] # for example, 1 > > How would I compare '1' with 2, 3, 3, 4? # Untested counts = {} for j in range(len(a)): x = a[j] count = 1 for k in range(j+1, len(a)): if x == a[k]: count += 1 else: counts[x] = count break > Do I need another duplicated list such as b = a and compare a[0] with > either b[0], b[1], b[2], b[3], b[4]? b = a doesn't create a duplicated list, it gives the same list a second name. Watch this: >>> a = [1, 2, 3] >>> b = a >>> b.append("Surprise!") >>> a [1, 2, 3, 'Surprise!'] b and a both refer to the same object, the list [1,2,3,'Surprise!']. To make a copy of the list, you need: b = a[:] But why bother, if all you're doing is comparisons and not modifying it? -- Steven D'Aprano From alan.gauld at btinternet.com Fri Jun 11 19:48:29 2010 From: alan.gauld at btinternet.com (ALAN GAULD) Date: Fri, 11 Jun 2010 10:48:29 -0700 (PDT) Subject: [Tutor] Looking for duplicates within a list [SOLVED] In-Reply-To: <4C1253F5.2090300@insightbb.com> References: <4C1240CE.7050807@insightbb.com> <4C1253F5.2090300@insightbb.com> Message-ID: <463.83642.qm@web86706.mail.ird.yahoo.com> > > counts = > > set(( item, mylist.count(item)) for item in mylist if mylist.count(item) > > Whee, this is great! I learned a lot today. I should have added that although thats a one liner in code terms it does involve iterating over the list twice - in count() - for each element. So it might not be very fast for big lists, certainly there are more efficient solutions if you don't mind writing more code. But for most lists you will likely find it is fast enough, certainly for 18 items! Alan G. From beachkid at insightbb.com Fri Jun 11 19:52:16 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 13:52:16 -0400 Subject: [Tutor] Looking for duplicates within a list [SOLVED] In-Reply-To: <2114901386686547039@unknownmsgid> References: <4C1240CE.7050807@insightbb.com> <201006120149.55173.steve@pearwood.info> <2114901386686547039@unknownmsgid> Message-ID: <4C1277D0.3000906@insightbb.com> Hugo Arts wrote: > On 11 jun 2010, at 17:49, Steven D'Aprano wrote: > > >> On Sat, 12 Jun 2010 12:58:19 am Alan Gauld wrote: >> >> >>> Have you looked at the count method of lists? >>> >>> Something like: >>> >>> counts = set(( item, mylist.count(item)) for item in mylist if >>> mylist.count(item) > 1) >>> >> That's a Shlemiel the Painter algorithm. >> >> http://www.joelonsoftware.com/articles/fog0000000319.html >> >> > > It is, but it's also very elegant and simple to understand. And it > works fine on small inputs. Everything is fast for small n. > > >>> Seems to work... >>> >> You say that now, but one day you will use it on a list of 100,000 >> items, and you'll wonder why it takes 45 minutes to finish, and curse >> Python for being slow. >> >> > > Actually, now that you know it is a shlemiel the painter's algorithm, > you won't have to wonder anymore. And you'll just say: "well, this > piece of code might need to handle huge lists someday, I'll use a > dictionary." > > I guess what I'm trying to say is: using code that performs bad in > situations that won't be encountered anyway is not inherently bad. > Otherwise, we'd all still be writing everything in C. > > The corrolary, of course, is that you should always know what the > performance characteristics of your code are, and what kind of data it > will handle. > > Hugo > > I appreciate your input. Thanks! Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: From beachkid at insightbb.com Fri Jun 11 19:53:54 2010 From: beachkid at insightbb.com (Ken G.) Date: Fri, 11 Jun 2010 13:53:54 -0400 Subject: [Tutor] Looking for duplicates within a list [SOLVED] In-Reply-To: References: <4C1240CE.7050807@insightbb.com> <201006120149.55173.steve@pearwood.info> <4C125FA5.8000403@insightbb.com> Message-ID: <4C127832.1010705@insightbb.com> davidheiserca at gmail.com wrote: > How about this? > > List = [1, 2, 3, 3, 3, 4, 5, 5] > for Item in list(set(List)): > print Item, List.count(Item) > > > > ----- Original Message ----- > *From:* Ken G. > *To:* Steven D'Aprano > *Cc:* tutor at python.org > *Sent:* Friday, June 11, 2010 9:09 AM > *Subject:* Re: [Tutor] Looking for duplicates within a list [SOLVED] > > > Steven D'Aprano wrote: >> On Sat, 12 Jun 2010 12:58:19 am Alan Gauld wrote: >> >> >>> Have you looked at the count method of lists? >>> >>> Something like: >>> >>> counts = set(( item, mylist.count(item)) for item in mylist if >>> mylist.count(item) > 1) >>> >> >> That's a Shlemiel the Painter algorithm. >> >> http://www.joelonsoftware.com/articles/fog0000000319.html >> >> >> >>> Seems to work... >>> >> >> You say that now, but one day you will use it on a list of 100,000 >> items, and you'll wonder why it takes 45 minutes to finish, and curse >> Python for being slow. >> > Hee, hee. Will investigate further. Thanks. > > Ken > > > ------------------------------------------------------------------------ > ___ > Oh, a nice one. Many thanks. Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: From alan.gauld at btinternet.com Fri Jun 11 20:19:52 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Fri, 11 Jun 2010 19:19:52 +0100 Subject: [Tutor] Looking for duplicates within a list [SOLVED] References: <4C1240CE.7050807@insightbb.com><201006120149.55173.steve@pearwood.info><4C125FA5.8000403@insightbb.com> Message-ID: wrote > How about this? > > List = [1, 2, 3, 3, 3, 4, 5, 5] > for Item in list(set(List)): > print Item, List.count(Item) Not bad and you don't need the convert back to list() But it doesn't filter out those items which are unique which the OP asked for. So I guess it becomes for item in set(List): n = List.count(item) if n > 1: print item, n which is still pretty clear. -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From knacktus at googlemail.com Fri Jun 11 21:42:35 2010 From: knacktus at googlemail.com (Knacktus) Date: Fri, 11 Jun 2010 21:42:35 +0200 Subject: [Tutor] What's the catch with ZopeDB? Message-ID: <4C1291AB.40804@googlemail.com> Hey everyone, I'm planning to create small application which manages product data e.g. parts of cars. There are quite some relations, e.g. - a car consists of certain assemblies, - an assembly consists of certatin parts, - a part has serveral documents which describe the part, e.g. a CAD document or material data. So, one could think of storing the data in a relational database. But now I start to think ... ;-): - I would just need some predefined queries which would be performed by Python code, of course. Maybe using an ORM. - Therefore, I don't think I need all the power and flexibility of SQL. - I will work with Python objects. Why should I translate to an relational schema "just" for persistence? - Performancewise, caching is probably much more sensitive than pure database performance. (That my guess...) To me, ZopeDB (a object database for Python) looks like an awesomely easy solution. I could save some brain power for the innovative part or drink more beer watching the soccer world cup. At the same moment, I wonder why anyone in the python world would go through the hassle of using relational databases unless forced. So, has anyone experience with ZopeDB? Are there some drawbacks I should be aware of before getting a book and dive in? (It sounds too good ;-)) Cheers, Jan From hugo.yoshi at gmail.com Fri Jun 11 21:59:45 2010 From: hugo.yoshi at gmail.com (Hugo Arts) Date: Fri, 11 Jun 2010 21:59:45 +0200 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <201006120328.31344.steve@pearwood.info> References: <4C1240CE.7050807@insightbb.com> <201006120149.55173.steve@pearwood.info> <2114901386686547039@unknownmsgid> <201006120328.31344.steve@pearwood.info> Message-ID: I really shouldn't, but I'll bite just this once. On Fri, Jun 11, 2010 at 7:28 PM, Steven D'Aprano wrote: > > Your idea of elegant and simple is not the same as mine. To me, I see > unnecessary work and unneeded complexity. A generator expression for a > beginner having trouble with the basics? Calling mylist.count(item) > *twice* for every item?! How is that possibly elegant? > What I mean by simple is that that line of code is the most obvious and direct translation of "a list of every item and how often it appears, for every item that appears more than once." I call it elegant because the code is even shorter than that English description while remaining readable, possibly even to someone with little programming experience. I'm making a judgement based on readability, not performance. Code that goes for performance in lieu of readability I'd call "clever," and that's not a compliment. Yes, it's an opinion. You disagree. That's fine. > [pedantic] > Not everything. Some things are inherently slow, for example: > > http://en.wikipedia.org/wiki/Busy_beaver > > A five-state Busy Beaver machine takes 47,176,870 steps to return, and a > six-state Busy Beaver takes 10**21132 steps to return. > > A slightly less extreme example is Ackermann's Function: > > http://en.wikipedia.org/wiki/Ackermann's_function > > where (for example) A(4,2) has over 19,000 digits. Calculating the > number of recursive steps needed to calculate that value is left as an > exercise. > [/pedantic] > > These are extreme examples, but the point is that there are tasks which > are hard even for small N. "Find N needles in a haystack" remains hard > even for N=1. > Now you're just arguing for the sake of being right (points for marking it [pedantic], I suppose). The busy beaver and Ackermann function have no bearing on this discussion whatsoever. If we're going to argue pedantically, the 1-state busy beaver (n=1) finishes in one step, and A(1,0) = A(0, 1) = 2. Even those are fast for small n, they just grow ridiculously quickly. Also, (pedantically), the problem "find needles in a haystack" grows in the size of the haystack, not the amount of needles. So the more appropriate n=1 version would be a haystack of size 1 with a needle in it. Which is quite easy. > (And before you suggest using a magnet, it's a *plastic* needle.) That solution is not in the spirit of the problem, and since I know that, I wouldn't bring it up. > > The problem is that situations that won't be encountered often *are* > encountered, long after the coder who introduced the poorly-performing > algorithm has moved on. > > Here's a real-life example, from Python itself: last September, on the > Python-Dev mailing list, Chris Withers reported a problem downloading a > file using Python's httplib module. For a file that took wget or > Internet Explorer approximately 2 seconds to download, it took Python > up to thirty MINUTES -- that's nearly a thousand times slower. > > Eventually Chris, with the help of others on the list, debugged the > problem down to a Shlemiel algorithm in the httplib code. Somebody > found a comment in the _read_chunked method that said: > > ? # XXX This accumulates chunks by repeated string concatenation, > ? # which is not efficient as the number or size of chunks gets big. > > So somebody used an algorithm which they KNEW was inefficient and slow, > it had been there for years, affecting who knows how many people, until > eventually somebody was annoyed sufficiently to do something about it. > And the sad thing is that avoiding repeated string concatenation is > easy and there was no need for it in the first place. > Estimating the size of your input is sometimes hard. That's a valid point. OTOH, that line of code takes maybe 10 seconds to write, and after profiling reveals it to be slow (you *are* profiling your code, right?) you can easily replace it with something more appropriate. Or your successor can, since he'll have no problem figuring out what it does. > > You've missed the point. It's not the language, you can write poorly > performing code in any language, and an O(N) algorithm in a slow > language will probably out-perform an O(N**2) or O(2**N) algorithm in a > fast language. > That wasn't the point I was trying to make. My point was that speed is not always the primary concern, and if it is, you shouldn't be writing code in python anyway, since it is always possible to write a program in C that performs better. Alan's code makes a trade-off between performance and readability. I'd call it the easiest to read solution so far. That's a trade-off that may or may not be appropriate. My point is that you shouldn't dismiss the code just because the algorithm sucks. You should only dismiss it because the algorithm sucks *and* your code will have to handle large inputs. Hugo From emile at fenx.com Fri Jun 11 22:07:47 2010 From: emile at fenx.com (Emile van Sebille) Date: Fri, 11 Jun 2010 13:07:47 -0700 Subject: [Tutor] What's the catch with ZopeDB? In-Reply-To: <4C1291AB.40804@googlemail.com> References: <4C1291AB.40804@googlemail.com> Message-ID: On 6/11/2010 12:42 PM Knacktus said... > So, has anyone experience with ZopeDB? Are there some drawbacks I should > be aware of before getting a book and dive in? (It sounds too good ;-)) > I've been using it as part of a couple applications I wrote 10 years ago that use zope. I'm not sure how my comments relate to non-zope usage or the recent versions so YMMV. The two things that bother me most are that without packing the database, it grows -- apparently without bound. It'll pack a 1Gb source DB down to 32Mb. Also, I once experienced corruption and found it impossible to recover the lost data, and I've a fair amount of experience recovering lost data even from unmountable partitions and drives that don't power up. I'm not opposed to the idea so I think I'd try it out, but those are issues I'd watch for. Emile From dkuhlman at rexx.com Sat Jun 12 00:10:43 2010 From: dkuhlman at rexx.com (Dave Kuhlman) Date: Fri, 11 Jun 2010 15:10:43 -0700 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: <4C1240CE.7050807@insightbb.com> References: <4C1240CE.7050807@insightbb.com> Message-ID: <20100611221043.GA56775@cutter.rexx.com> On Fri, Jun 11, 2010 at 09:57:34AM -0400, Ken G. wrote: > > > for j in range (0, 5): > x = a[0] # for example, 1 One picky, little point. I've seen several solutions in this thread that included something like the following: for i in range(len(mylist)): val = mylist[i] mylist[i] = f(val) o o o That works fine, but ... You can do this a bit more easily by using the "enumerate" built-in function. It provides that index. Example: for i, val in enumerate(mylist): mylist[i] = f(val) o o o See http://docs.python.org/library/functions.html#enumerate - Dave -- Dave Kuhlman http://www.rexx.com/~dkuhlman From dkuhlman at rexx.com Sat Jun 12 00:27:44 2010 From: dkuhlman at rexx.com (Dave Kuhlman) Date: Fri, 11 Jun 2010 15:27:44 -0700 Subject: [Tutor] What's the catch with ZopeDB? In-Reply-To: <4C1291AB.40804@googlemail.com> References: <4C1291AB.40804@googlemail.com> Message-ID: <20100611222744.GB56775@cutter.rexx.com> On Fri, Jun 11, 2010 at 09:42:35PM +0200, Knacktus wrote: > > To me, ZopeDB (a object database for Python) looks like an awesomely > easy solution. I could save some brain power for the innovative part or > drink more beer watching the soccer world cup. At the same moment, I > wonder why anyone in the python world would go through the hassle of > using relational databases unless forced. > > So, has anyone experience with ZopeDB? Are there some drawbacks I should > be aware of before getting a book and dive in? (It sounds too good ;-)) > Jan - If you are evaluating alternative solutions, you might also look into Django models. There have been some very positive comments about Django on this list. And, Django models can be used outside of the Django Web applications. Also, Django models are reasonably object oriented. A Django model/DB can sit on top of several different relational database engines, for example, PostgreSQL, MySQL, sqlite3, etc. See: http://docs.djangoproject.com/en/1.2/#the-model-layer http://www.djangobook.com/en/2.0/chapter05/ - Dave -- Dave Kuhlman http://www.rexx.com/~dkuhlman From eldonjr at hotmail.com Sat Jun 12 03:13:31 2010 From: eldonjr at hotmail.com (Eldon Londe Mello Junior) Date: Fri, 11 Jun 2010 22:13:31 -0300 Subject: [Tutor] Python a substitute/alternative for PhP? In-Reply-To: <20100611222744.GB56775@cutter.rexx.com> References: <4C1291AB.40804@googlemail.com>, <20100611222744.GB56775@cutter.rexx.com> Message-ID: Hi there, If you care to listen to my story and fully help me out, just keep on reading }else{ move to the final question :) I'm just finishing an introductory course on PhP and MySQL (HTML, CSS and Javascript basics included). That's a typical first step to novice programmers in Brazil. However, I've been reading a lot about programming languages and stuff in order to make the best choice as I don't want to spend much time learning unnecessary things I won't need in the future. Thus, I decided I want to be a contributor for the GNU/LINUX community and, of course, become sort of an opensource-solutions professional programmer. And if I got it right, python would the most adequate language for me to reach my goals. Only a few programmers in Brazil are familiar with python though. As I said before, most beginners start with PhP and stick with it or go for JAVA or MS proprietary languages. Actually, you can only learn python on your own around here as no college or private institutes offer python courses. As you may see it coming, the big question for me is: should I stick with PHP as most people here (those fond of free software) or Python is or would be a better choice for me? FINAL QUESTION> Is Python a substitute for PHP? I mean, can I start learning python by trying to do the things I've learned with PHP? Are they different anyhow or they actually compete against each other? Thanks in advance, advice on which steps to take to reach my career goals would be very appreciated as well! Eldon. > Date: Fri, 11 Jun 2010 15:27:44 -0700 > From: dkuhlman at rexx.com > To: Tutor at python.org > Subject: Re: [Tutor] What's the catch with ZopeDB? > > On Fri, Jun 11, 2010 at 09:42:35PM +0200, Knacktus wrote: > > > > > To me, ZopeDB (a object database for Python) looks like an awesomely > > easy solution. I could save some brain power for the innovative part or > > drink more beer watching the soccer world cup. At the same moment, I > > wonder why anyone in the python world would go through the hassle of > > using relational databases unless forced. > > > > So, has anyone experience with ZopeDB? Are there some drawbacks I should > > be aware of before getting a book and dive in? (It sounds too good ;-)) > > > > Jan - > > If you are evaluating alternative solutions, you might also look > into Django models. There have been some very positive comments > about Django on this list. And, Django models can be used outside > of the Django Web applications. Also, Django models are reasonably > object oriented. A Django model/DB can sit on top of several > different relational database engines, for example, PostgreSQL, MySQL, > sqlite3, etc. > > See: > > http://docs.djangoproject.com/en/1.2/#the-model-layer > http://www.djangobook.com/en/2.0/chapter05/ > > - Dave > > -- > Dave Kuhlman > http://www.rexx.com/~dkuhlman > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor _________________________________________________________________ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. https://signup.live.com/signup.aspx?id=60969 -------------- next part -------------- An HTML attachment was scrubbed... URL: From mehgcap at gmail.com Sat Jun 12 03:33:46 2010 From: mehgcap at gmail.com (Alex Hall) Date: Fri, 11 Jun 2010 21:33:46 -0400 Subject: [Tutor] Python a substitute/alternative for PhP? In-Reply-To: References: <4C1291AB.40804@googlemail.com> <20100611222744.GB56775@cutter.rexx.com> Message-ID: Personally, I would learn Python. My college does not offer Python either, so I had to learn what I know on my own(of course, by that I mean constantly pestering this and other of the amazing Python email lists). PHP is fine in itself, but, after using it, Java, and intros to a few other languages, nothing has been able to beat Python's ease of use, massive extensibility (there is a package to let you do just about anything you want), and support community. It is a great language and, especially if you plan to stick with desktop applications, I think it is much easier than a language like C++ or Java. Your life will be even easier than mine since you are going to be on Linux; I believe most Linux distros come with Python, while Windows does not, so what you make can be distributed as scripts while I have to use a program like py2exe and package the entire Python interpreter. Anyway, just my thoughts. Note that I am still in college for my computer science degree and am in no way a professional programmer, just someone who has waded in several languages and found Python to be the only one worth diving into all the way. On 6/11/10, Eldon Londe Mello Junior wrote: > > Hi there, > > If you care to listen to my story and fully help me out, just keep on > reading }else{ move to the final question :) > > I'm just finishing an introductory course on PhP and MySQL (HTML, CSS and > Javascript basics included). That's a typical first step to novice > programmers in Brazil. > > However, I've been reading a lot about programming languages and stuff in > order to make the best choice as I don't want to spend much time learning > unnecessary things I won't need in the future. > > Thus, I decided I want to be a contributor for the GNU/LINUX community and, > of course, become sort of an opensource-solutions professional programmer. > And if I got it right, python would the most adequate language for me to > reach my goals. > > Only a few programmers in Brazil are familiar with python though. As I said > before, most beginners start with PhP and stick with it or go for JAVA or MS > proprietary languages. Actually, you can only learn python on your own > around here as no college or private institutes offer python courses. > > As you may see it coming, the big question for me is: should I stick with > PHP as most people here (those fond of free software) or Python is or would > be a better choice for me? > > FINAL QUESTION> Is Python a substitute for PHP? I mean, can I start learning > python by trying to do the things I've learned with PHP? Are they different > anyhow or they actually compete against each other? > > Thanks in advance, advice on which steps to take to reach my career goals > would be very appreciated as well! > > Eldon. > > > > > >> Date: Fri, 11 Jun 2010 15:27:44 -0700 >> From: dkuhlman at rexx.com >> To: Tutor at python.org >> Subject: Re: [Tutor] What's the catch with ZopeDB? >> >> On Fri, Jun 11, 2010 at 09:42:35PM +0200, Knacktus wrote: >> >> > >> > To me, ZopeDB (a object database for Python) looks like an awesomely >> > easy solution. I could save some brain power for the innovative part or >> > drink more beer watching the soccer world cup. At the same moment, I >> > wonder why anyone in the python world would go through the hassle of >> > using relational databases unless forced. >> > >> > So, has anyone experience with ZopeDB? Are there some drawbacks I should >> > >> > be aware of before getting a book and dive in? (It sounds too good ;-)) >> > >> >> Jan - >> >> If you are evaluating alternative solutions, you might also look >> into Django models. There have been some very positive comments >> about Django on this list. And, Django models can be used outside >> of the Django Web applications. Also, Django models are reasonably >> object oriented. A Django model/DB can sit on top of several >> different relational database engines, for example, PostgreSQL, MySQL, >> sqlite3, etc. >> >> See: >> >> http://docs.djangoproject.com/en/1.2/#the-model-layer >> http://www.djangobook.com/en/2.0/chapter05/ >> >> - Dave >> >> -- >> Dave Kuhlman >> http://www.rexx.com/~dkuhlman >> _______________________________________________ >> Tutor maillist - Tutor at python.org >> To unsubscribe or change subscription options: >> http://mail.python.org/mailman/listinfo/tutor > > _________________________________________________________________ > Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. > https://signup.live.com/signup.aspx?id=60969 -- Have a great day, Alex (msg sent from GMail website) mehgcap at gmail.com; http://www.facebook.com/mehgcap From steve at pearwood.info Sat Jun 12 04:38:54 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Sat, 12 Jun 2010 12:38:54 +1000 Subject: [Tutor] Looking for duplicates within a list In-Reply-To: References: <4C1240CE.7050807@insightbb.com> <201006120328.31344.steve@pearwood.info> Message-ID: <201006121238.55555.steve@pearwood.info> On Sat, 12 Jun 2010 05:59:45 am Hugo Arts wrote: [...] Putting aside all the theoretical arguments, and getting to an actual, real-life example: > > So somebody used an algorithm which they KNEW was inefficient and > > slow, it had been there for years, affecting who knows how many > > people, until eventually somebody was annoyed sufficiently to do > > something about it. And the sad thing is that avoiding repeated > > string concatenation is easy and there was no need for it in the > > first place. > > Estimating the size of your input is sometimes hard. That's a valid > point. OTOH, that line of code takes maybe 10 seconds to write, and > after profiling reveals it to be slow (you *are* profiling your code, > right?) you can easily replace it with something more appropriate. Or > your successor can, since he'll have no problem figuring out what it > does. I beg to differ. The incident with httplib is actual, real-life evidence that your caviler attitude towards poor algorithms is bad advice. You wave your hands and say "Oh well, it doesn't matter, because somebody will find the slowdown and easily fix it". But in real life, it isn't that simple, not even in Open Source software let alone proprietary software where you might not have access to the source and the vendor might not care. (Has Microsoft yet fixed the ridiculously slow behaviour of the Trash Can when it has thousands of items in it?) I was mistaken when I said Chris Withers reported this performance bug in September. He actually first raised it with the Python-Dev team in early August: http://mail.python.org/pipermail/python-dev/2009-August/thread.html#91125 http://mail.python.org/pipermail/python-dev/2009-September/thread.html#91584 So this took AT LEAST a month elapsed time, with multiple people contributing, at least two different bug reports involved (and possibly five), and who knows how many hours debugging to solve this. Once the issue was identified, the solution was trivial: http://svn.python.org/view/python/trunk/Lib/httplib.py?r1=74523&r2=74655 but it took a lot of effort to identify the issue. As Guido van Rossum himself said, this was an embarrassment. The fix was entirely trivial, and there was no good reason to write the Shlemiel algorithm in the first place, especially since the author apparently knew it was a Shlemiel algorithm. Perhaps he too thought it was "more elegant" and that somebody else would "easily" deal with the problems that it caused. The poorly-performing httplib code has been in at least three major releases of CPython (2.4 to 2.6) and possibly more, but apparently due to differences in realloc it only affected Windows users. So once you've run into the bug, your *second* problem is that other people say "It works for me, it must be your network". It is not true that "he'll have no problem figuring out what it does". In code of any complexity, you can run into multiple problems and wild-goose-chases. This is a good example. Read the thread and see how many different ideas people had: they blamed the proxy, they blamed a pre-existing bug in sockets, they blamed buffer sizes. Nobody publicly blamed "third-party drivers", but I bet you somebody was thinking it. I think you have a very rosy view of how easy it is to debug performance issues. Debugging is hard. Debugging performance problems is ten times harder. Avoiding bad algorithms isn't premature optimization, it is thinking ahead. There's a fine line between them, I agree, but with the risks of hard-to-debug performance degradation caused by O(N**2) algorithms you should have a *seriously* compelling reason for using one, and not just because it's "good enough for small N" or "its a one-liner". On modern desktop or laptop hardware, I would expect small N to mean multiple hundreds or even thousands, not a dozen or two. This isn't 1985 when desktop computers couldn't count past 32768 and 1000 items was a lot. Today, large N is tens of millions. Huge is hundreds of millions, at which point I start worrying about paging into virtual memory more than the algorithm, because memory paging is an O(N**2) (or worse!) algorithm too. [...] > That wasn't the point I was trying to make. My point was that speed > is not always the primary concern, and if it is, you shouldn't be > writing code in python anyway, since it is always possible to write a > program in C that performs better. It is noteworthy the PyPy people use JIT compilation of Python code to beat the pants off CPython speed, and their audacious aim is to be *faster* than C, at least for some things. It is possible to write Python programs that run faster than the equivalent program written in optimized C. http://news.ycombinator.com/item?id=1379382 > Alan's code makes a trade-off between performance and readability. > I'd call it the easiest to read solution so far. Really? I think its readability is pretty poor, and nowhere near as clear as an explicit loop. Especially for a beginner who might not even know what a generator expression is. There's too much stuff in one line, making it hard to read. It does the same work multiple times instead of once. Instead of the one-liner: counts = set(( item, mylist.count(item)) for item in mylist if mylist.count(item) > 1) I think a two-liner is *far* clearer: counts = ((item, mylist.count(item)) for item in set(mylist)) counts = [t for t in counts if t[1] > 1] It's still has the awful O(N**2) performance, but it is nearly 25% faster (for N=18) by my tests, and is easier to read. And by some happy accident, it keeps the order of the original sorted list: >>> mylist = [1, 2, 2, 3, 3, 5, 6, 19, 21, 21, 23, ... 25, 25, 25, 26, 26, 31, 39] >>> counts = ((item, mylist.count(item)) for item in set(mylist)) >>> counts = [t for t in counts if t[1] > 1] >>> counts [(2, 2), (3, 2), (21, 2), (25, 3), (26, 2)] -- Steven D'Aprano From amartin7211 at gmail.com Sat Jun 12 06:50:26 2010 From: amartin7211 at gmail.com (Andrew Martin) Date: Sat, 12 Jun 2010 00:50:26 -0400 Subject: [Tutor] Problems with Importing into the Python Shell Message-ID: Hey, everyone, I am new to programming and just downloaded Python 2.6 onto my windows vista laptop. I am attempting to follow 4.11 of the tutorial called "How to Think Like a Computer Scientist: Learning with Python v2nd Edition documentation" ( http://openbookproject.net/thinkcs/python/english2e/ch04.html). However, I am having some trouble. First off, I do not understand how to import things into the python shell. I have a script I saved as chap03.py, but when I try to import it into the python shell i get an error like this: >>> from chap03 import * Traceback (most recent call last): File "", line 1, in from chap03 import * File "C:/Python26\chap03.py", line 2 print param param ^ SyntaxError: invalid syntax >>> The chap03.py file is a simple one that looks like this: def print_twice(param): print param param My second problem is that I need to install and import GASP in order to follow the tutorial. When I tried to do import it, I ran into an error like this: >>> from gasp import * Traceback (most recent call last): File "", line 1, in from gasp import * File "C:\Python26\lib\site-packages\gasp\__init__.py", line 1, in from api import * File "C:\Python26\lib\site-packages\gasp\api.py", line 1, in import backend File "C:\Python26\lib\site-packages\gasp\backend.py", line 7, in except ImportError: raise 'Pygame is not installed. Please install it.' TypeError: exceptions must be old-style classes or derived from BaseException, not str >>> Can anybody help me with this? Thanks a lot P.S. SORRY FOR THE LONG EMAIL -------------- next part -------------- An HTML attachment was scrubbed... URL: From breamoreboy at yahoo.co.uk Sat Jun 12 09:39:09 2010 From: breamoreboy at yahoo.co.uk (Mark Lawrence) Date: Sat, 12 Jun 2010 08:39:09 +0100 Subject: [Tutor] Problems with Importing into the Python Shell In-Reply-To: References: Message-ID: On 12/06/2010 05:50, Andrew Martin wrote: > Hey, everyone, I am new to programming and just downloaded Python 2.6 onto > my windows vista laptop. I am attempting to follow 4.11 of the tutorial > called "How to Think Like a Computer Scientist: Learning with Python v2nd > Edition documentation" ( > http://openbookproject.net/thinkcs/python/english2e/ch04.html). However, I > am having some trouble. First off, I do not understand how to import things > into the python shell. I have a script I saved as chap03.py, but when I try > to import it into the python shell i get an error like this: > >>>> from chap03 import * This is generally considered bad practice, I'll let you do some research to find out why. :) > > Traceback (most recent call last): > File "", line 1, in > from chap03 import * > File "C:/Python26\chap03.py", line 2 > print param param > ^ > SyntaxError: invalid syntax >>>> > > The chap03.py file is a simple one that looks like this: > def print_twice(param): > print param param One of the great advantages of Python is trying things from an interactive prompt, so let's go. c:\Users\Mark\python>python Python 2.6.5 (r265:79096, Mar 19 2010, 21:48:26) [MSC v.1500 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> def print_twice(param): ... print param param File "", line 2 print param param ^ SyntaxError: invalid syntax So it is! What's print_twice trying to do, let's guess? >>> def print_twice(param): ... print param, param ... >>> print_twice('Hi Andrew') Hi Andrew Hi Andrew >>> Better! See how I slotted that comma into the function print_twice, just hope my guess is right. So run up some editor/IDE and slap that comma in there, it should at least keep you going. > > My second problem is that I need to install and import GASP in order to > follow the tutorial. When I tried to do import it, I ran into an error like > this: >>>> from gasp import * > > Traceback (most recent call last): The line above basically says "start reading from the bottom up" > File "", line 1, in > from gasp import * > File "C:\Python26\lib\site-packages\gasp\__init__.py", line 1, in > from api import * > File "C:\Python26\lib\site-packages\gasp\api.py", line 1, in > import backend > File "C:\Python26\lib\site-packages\gasp\backend.py", line 7, in > except ImportError: raise 'Pygame is not installed. Please install it.' > TypeError: exceptions must be old-style classes or derived from > BaseException, not str The TypeError means exactly what it says. The ImportError is trying to raise an exception, but what follows is a string type, not an exception type. Just install Pygame to get yourself going, at some point in the tutorial you're bound to run into exception handling. >>>> > > Can anybody help me with this? > > Thanks a lot > > P.S. SORRY FOR THE LONG EMAIL By some standards this doesn't even qualify as short, it's just a snippet. > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor HTH, and keep asking as Python lists are renowned for their friendlyness. Mark Lawrence. From steve at pearwood.info Sat Jun 12 10:33:23 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Sat, 12 Jun 2010 18:33:23 +1000 Subject: [Tutor] Problems with Importing into the Python Shell In-Reply-To: References: Message-ID: <201006121833.24205.steve@pearwood.info> On Sat, 12 Jun 2010 02:50:26 pm Andrew Martin wrote: > >>> from chap03 import * > > Traceback (most recent call last): > File "", line 1, in > from chap03 import * > File "C:/Python26\chap03.py", line 2 > print param param > ^ > SyntaxError: invalid syntax This tells you exactly what the error is: a syntax error in your module chap03, which prevents Python from importing it. `print a b` is not valid Python syntax. Python can't correct the error, because it doesn't know if you mean print param+param, or param,param or "param param" or something else, and it refuses to guess. > The chap03.py file is a simple one that looks like this: > def print_twice(param): > print param param The print statement takes a comma-separated list of things to print: print param, param > My second problem is that I need to install and import GASP in order > to follow the tutorial. When I tried to do import it, I ran into an > error like > > this: > >>> from gasp import * > > Traceback (most recent call last): > File "", line 1, in > from gasp import * > File "C:\Python26\lib\site-packages\gasp\__init__.py", line 1, in > from api import * > File "C:\Python26\lib\site-packages\gasp\api.py", line 1, in > import backend > File "C:\Python26\lib\site-packages\gasp\backend.py", line 7, in > except ImportError: raise 'Pygame is not installed. Please > install it.' TypeError: exceptions must be old-style classes or > derived from BaseException, not str Here you have two problems. The first problem is that you need to have Pygame installed, and you don't, or it is installed in such a place that Python 2.6 can't see it. The second is that the version of gasp you are using has a bug in it, possibly because you're using an old version. In the very early days of Python, it used string exceptions: to raise an error message, you would say: raise "this is an error message" For various reasons, this was not very satisfactory, and over the years these string exceptions were discouraged, then flagged as officially deprecated, then Python would print an warning message when you used them, and finally in Python 2.6 they because prohibited: >>> raise "this is an error" Traceback (most recent call last): File "", line 1, in TypeError: exceptions must be classes or instances, not str So the version of gasp you are using pre-dates Python 2.6, and contains obsolete code that does not run correctly. Your work-arounds, in order of best-to-worst ideas: (1) Install an updated version of gasp that works with Python 2.6; (2) Install Python 2.5 and use that; or (3) Hack your copy of gasp to fix the bug. Of course, since you're a beginner, option 3 (not very desirable at the best of times!) is virtually impossible. Good luck! However, there is one little ray of sunshine. If you install Pygame, gasp should successfully import it and therefore not try to raise a string exception, and the second error will disappear all on its own. (But who knows how many more little landmines are waiting...) -- Steven D'Aprano From advertising at robbstucky.net Fri Jun 11 23:12:27 2010 From: advertising at robbstucky.net (Advertising Department) Date: Fri, 11 Jun 2010 17:12:27 -0400 Subject: [Tutor] (no subject) Message-ID: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> #!/Library/Frameworks/Python.framework/Versions/Current/bin/pythonw """still thinking in imperative" """ ## obviously this is a bad construct. ## Can someone suggest a pythonesque way of doing this? def getid(): response = raw_input('prompt') if response not in [ "", "y", "Y", "yes"] : getid() # ouch print "continue working" # do more stuff # do more stuff getid() dosomething() getid() dosomethingelse() ## obviously this is a bad construct. ## Can someone give me a pythonesque way of doing this? From zubin.mithra at gmail.com Fri Jun 11 21:27:39 2010 From: zubin.mithra at gmail.com (Zubin Mithra) Date: Sat, 12 Jun 2010 00:57:39 +0530 Subject: [Tutor] lib2to3 fixers Message-ID: Hey everyone, I just discovered that the following construct does not work in Py3k. >>> string.maketrans('-', '_') However, the following works, >>> str.maketrans('-', '_') When i try to convert a python module containing the above construct, it does not get modified in a way such that it could run on Python 3.0 I`m trying to automate the conversion of making the module Py3k compatible and so I guess i`m left with two options. 1. replace string.maketrans() with a function which is compatible in both Python 2.x and 3.0 ; as of now I`m unaware of such a construct. 2. write a fixer for doing this which I could use. I could`nt find any good tutorials out there on writing fixers, i`d be grateful if you could point me to any. Thankx in advance, cheers zubin From rdmoores at gmail.com Sat Jun 12 10:50:21 2010 From: rdmoores at gmail.com (Richard D. Moores) Date: Sat, 12 Jun 2010 01:50:21 -0700 Subject: [Tutor] winsound.Beep(500,500) "Failed to beep" Message-ID: >>> import winsound >>> winsound.Beep(500,500) Traceback (most recent call last): File "", line 1, in RuntimeError: Failed to beep >>> Vista, Python 3.1 Any ideas? Dick Moores -------------- next part -------------- An HTML attachment was scrubbed... URL: From ljmamoreira at gmail.com Sat Jun 12 11:20:01 2010 From: ljmamoreira at gmail.com (Jose Amoreira) Date: Sat, 12 Jun 2010 10:20:01 +0100 Subject: [Tutor] (no subject) In-Reply-To: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> References: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> Message-ID: <201006121020.01253.ljmamoreira@gmail.com> On Friday, June 11, 2010 10:12:27 pm Advertising Department wrote: > #!/Library/Frameworks/Python.framework/Versions/Current/bin/pythonw > """still thinking in imperative" > """ > > ## obviously this is a bad construct. > ## Can someone suggest a pythonesque way of doing this? > > > def getid(): > response = raw_input('prompt') > if response not in [ "", "y", "Y", "yes"] : > getid() # ouch > print "continue working" > # do more stuff > # do more stuff > > > getid() > dosomething() > getid() > dosomethingelse() > > > ## obviously this is a bad construct. > ## Can someone give me a pythonesque way of doing this? > Using recursion for validation, that doesn't sound right. I would rather do it with a simple while cycle: response="any invalid string" while response not in ["","y","Y","yes"]: response = raw_input("prompt") Hope this helps Jos? From kaushalshriyan at gmail.com Sat Jun 12 11:37:12 2010 From: kaushalshriyan at gmail.com (Kaushal Shriyan) Date: Sat, 12 Jun 2010 15:07:12 +0530 Subject: [Tutor] New to Programming Message-ID: Hi, I am absolutely new to programming language. Dont have any programming experience. Can some one guide me please. is python a good start for novice. Thanks, Kaushal From davea at ieee.org Sat Jun 12 12:34:31 2010 From: davea at ieee.org (Dave Angel) Date: Sat, 12 Jun 2010 06:34:31 -0400 Subject: [Tutor] New to Programming In-Reply-To: References: Message-ID: <4C1362B7.6070702@ieee.org> Kaushal Shriyan wrote: > Hi, > > I am absolutely new to programming language. Dont have any programming > experience. Can some one guide me please. is python a good start for > novice. > > Thanks, > > Kaushal > > Like nearly all questions, the answer is "it depends." Mainly, it depends on what your goal is. In my case, I made my living with programming, for many years. And in the process, learned and used about 35 languages, plus a few more for fun. I wish I had discovered Python much earlier, though it couldn't have been my first, since it wasn't around. But it'd have been much better than Fortran was, for learning. So tell us about your goals. Abstract knowledge, console utilities, gui development, games, web development, networking communication, ... Next, you might want to evaluate what you already know. There are a lot of non-programming things that a programmer needs to understand. If you already know many of them, that's a big head start. If you already know how to administer a Linux system, you're already a programmer and didn't know it. If you write complex formulas for Excel, you're a programmer. If you already know modus ponens, and understand what a contrapositive is, you've got a head start towards logic (neither is a programming subject, just a start towards logical thinking). If you've worked on a large document, and kept backups of incremental versions, so you could rework the current version based on earlier ones, that's a plus. If you know why a file's timestamp might change when you copy it from hard disk to a USB drive and back again, you've got a head start. If you know why it might have a different timestamp when you look at it six months from now without changing it, you've got a head start. If you're using Windows and never used a command prompt, you have a ways to go. If you don't know what a file really is, or how directories are organized, you have a ways to go. And if you think a computer is intelligent, you have a long way to go. Python is a powerful tool. But if you're totally new to programming, it can also be daunting. And most people have no idea how easy some programs are, nor how hard some other programs are, to build. In any case, some of the things recommending Python as a first language are: 1) an interactive interpreter - you can experiment, trivially 2) very fast turnaround, from the time you make a change, till you can see how it works. This can be true even for large programs 3) this mailing list DaveA From sudipb at sudipb.com Sat Jun 12 12:34:44 2010 From: sudipb at sudipb.com (Sudip Bhattacharya) Date: Sat, 12 Jun 2010 16:04:44 +0530 Subject: [Tutor] Adding line numbers to a Python Script Message-ID: I quote this example (and the problem that I am facing trying to understand) from the book "Beginning Python - From Novice to Professional" by Magnus Lie Hetland Page 227 # numberlines.py import fileinput........................(1) for line in fileinput.input(inplace = true)............(2) line = line.rstrip()........................................(3) num=fileinput.lineno()..................................(4) print '%-40s #%2i' %(line,num).....................(5) Question: Please help me understand: Line (3) - Are we stripping the entire line of code first, inserting the code at the end (line (5)) and then placing it back at the same place ? Line (5) - What does the individual characters in the expression "Print '%-40s #%2i' %(line,num)" mean ? - '-40s' : is this the space [what does "-40s" mean] that we are creating post - which the line nos is inserted "#%2i" ? - What does '%2" mean ? - Is that 2 cursor spaces of width ? Much thanks in advance... -- Thanks and regards, Sudip Bhattacharya Mobile: +91 9999 100 706 Home Land line: +91 11 22237561 Office Land line: +91 0124 4321078 eMail ID: sudipb at sudipb.com; sudipb at gmail.com Please visit my website at: www.sudipb.com -------------- next part -------------- An HTML attachment was scrubbed... URL: From __peter__ at web.de Sat Jun 12 13:19:37 2010 From: __peter__ at web.de (Peter Otten) Date: Sat, 12 Jun 2010 13:19:37 +0200 Subject: [Tutor] Looking for duplicates within a list References: <4C1240CE.7050807@insightbb.com> Message-ID: Ken G. wrote: > I have been working on this problem for several days and I am not making > any progress. I have a group of 18 number, in ascending order, within a > list. They ranged from 1 to 39. Some numbers are duplicated as much as > three times or as few as none. > > I started with one list containing the numbers. For example, they are > listed as like below: > > a = [1, 2, 3, 3, 4] > > I started off with using a loop: > > for j in range (0, 5): > x = a[0] # for example, 1 > > How would I compare '1' with 2, 3, 3, 4? > > Do I need another duplicated list such as b = a and compare a[0] with > either b[0], b[1], b[2], b[3], b[4]? > > Or do I compare a[0] with a[1], a[2], a[3], a[4]? > > In any event, if a number is listed more than once, I would like to know > how many times, such as 2 or 3 times. For example, '3' is listed twice > within a list. I haven't seen a solution that takes advantage of the fact that the numbers are sorted, so here's one: >>> items = [1, 2, 3, 3, 4] >>> value = items[0] >>> n = 0 >>> result = [] >>> for item in items: ... if value != item: ... print value, "-->", n ... value = item ... n = 1 ... else: ... n += 1 ... 1 --> 1 2 --> 1 3 --> 2 >>> print value, "-->", n 4 --> 1 Python has a cool feature called generator that allows you to encapsulate the above nicely: >>> def count_runs(items): ... it = iter(items) ... value = next(it) ... n = 1 # next consumes one item ... for item in it: # the for loop starts with the second item ... if value != item: ... yield value, n ... value = item ... n = 1 ... else: ... n += 1 ... yield value, n ... >>> for v, n in count_runs([1, 1, 1, 2, 2, 3, 4, 4, 4, 4]): ... print v, "-->", n ... 1 --> 3 2 --> 2 3 --> 1 4 --> 4 Finally, there is itertools.groupby() which allows you to simplify the implementation count_runs(): >>> from itertools import groupby >>> def count_runs2(items): ... for key, group in groupby(items): ... yield key, sum(1 for _ in group) ... >>> for v, n in count_runs2([1, 1, 1, 2, 2, 3, 4, 4, 4, 4]): ... print v, "-->", n ... 1 --> 3 2 --> 2 3 --> 1 4 --> 4 Peter From mehgcap at gmail.com Sat Jun 12 14:13:18 2010 From: mehgcap at gmail.com (Alex Hall) Date: Sat, 12 Jun 2010 08:13:18 -0400 Subject: [Tutor] winsound.Beep(500,500) "Failed to beep" In-Reply-To: References: Message-ID: Not that it helps much, but using win7x64 and Python 2.6 it works as expected. Possibly your sound card? Update drivers? On 6/12/10, Richard D. Moores wrote: >>>> import winsound >>>> winsound.Beep(500,500) > Traceback (most recent call last): > File "", line 1, in > RuntimeError: Failed to beep >>>> > > Vista, Python 3.1 > > Any ideas? > > Dick Moores > -- Have a great day, Alex (msg sent from GMail website) mehgcap at gmail.com; http://www.facebook.com/mehgcap From bgailer at gmail.com Sat Jun 12 17:05:52 2010 From: bgailer at gmail.com (bob gailer) Date: Sat, 12 Jun 2010 11:05:52 -0400 Subject: [Tutor] Better construct? (was no subject) In-Reply-To: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> References: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> Message-ID: <4C13A250.5020405@gmail.com> On 6/11/2010 5:12 PM, Advertising Department wrote: Please supply a meaningful subject. > #!/Library/Frameworks/Python.framework/Versions/Current/bin/pythonw > """still thinking in imperative" > """ > > ## obviously this is a bad construct. Why is it "obvious"? What is "this"? Are you referring to the function, to the mainline program, or what? > ## Can someone suggest a pythonesque way of doing this? > > > def getid(): > response = raw_input('prompt') > if response not in [ "", "y", "Y", "yes"] : > getid() # ouch > print "continue working" > # do more stuff > # do more stuff > > > getid() > dosomething() > getid() > dosomethingelse() > > > ## obviously this is a bad construct. > ## Can someone give me a pythonesque way of doing this? One improvement - response.lower().startswith("yes") will cover all your cases. You can collect functions in a sequence, then iterate over it. This allows for easy expansion (when you decide to add another function). funcs = (dosomething(), dosomethingelse()) for func in funcs: getid() func() -- Bob Gailer 919-636-4239 Chapel Hill NC From jdeltoro1973 at gmail.com Sat Jun 12 19:24:37 2010 From: jdeltoro1973 at gmail.com (Juan Jose Del Toro) Date: Sat, 12 Jun 2010 12:24:37 -0500 Subject: [Tutor] Python a substitute/alternative for PhP? In-Reply-To: References: <4C1291AB.40804@googlemail.com> <20100611222744.GB56775@cutter.rexx.com> Message-ID: 2010/6/11 Alex Hall > Personally, I would learn Python. My college does not offer Python > either, so I had to learn what I know on my own(of course, by that I > mean constantly pestering this and other of the amazing Python email > lists). PHP is fine in itself, but, after using it, Java, and intros > to a few other languages, nothing has been able to beat Python's ease > of use, massive extensibility (there is a package to let you do just > about anything you want), and support community. It is a great > language and, especially if you plan to stick with desktop > applications, I think it is much easier than a language like C++ or > Java. Your life will be even easier than mine since you are going to > be on Linux; I believe most Linux distros come with Python, while > Windows does not, so what you make can be distributed as scripts while > I have to use a program like py2exe and package the entire Python > interpreter. > Anyway, just my thoughts. Note that I am still in college for my > computer science degree and am in no way a professional programmer, > just someone who has waded in several languages and found Python to be > the only one worth diving into all the way. > > On 6/11/10, Eldon Londe Mello Junior wrote: > > > > Hi there, > > > > If you care to listen to my story and fully help me out, just keep on > > reading }else{ move to the final question :) > > > > I'm just finishing an introductory course on PhP and MySQL (HTML, CSS and > > Javascript basics included). That's a typical first step to novice > > programmers in Brazil. > > > > However, I've been reading a lot about programming languages and stuff in > > order to make the best choice as I don't want to spend much time learning > > unnecessary things I won't need in the future. > > > > Thus, I decided I want to be a contributor for the GNU/LINUX community > and, > > of course, become sort of an opensource-solutions professional > programmer. > > And if I got it right, python would the most adequate language for me to > > reach my goals. > > > > Only a few programmers in Brazil are familiar with python though. As I > said > > before, most beginners start with PhP and stick with it or go for JAVA or > MS > > proprietary languages. Actually, you can only learn python on your own > > around here as no college or private institutes offer python courses. > > > > As you may see it coming, the big question for me is: should I stick with > > PHP as most people here (those fond of free software) or Python is or > would > > be a better choice for me? > > > > FINAL QUESTION> Is Python a substitute for PHP? I mean, can I start > learning > > python by trying to do the things I've learned with PHP? Are they > different > > anyhow or they actually compete against each other? > > > > Thanks in advance, advice on which steps to take to reach my career goals > > would be very appreciated as well! > > > > Eldon. > > > > > > > > > > > >> Date: Fri, 11 Jun 2010 15:27:44 -0700 > >> From: dkuhlman at rexx.com > >> To: Tutor at python.org > >> Subject: Re: [Tutor] What's the catch with ZopeDB? > >> > >> On Fri, Jun 11, 2010 at 09:42:35PM +0200, Knacktus wrote: > >> > >> > > >> > To me, ZopeDB (a object database for Python) looks like an awesomely > >> > easy solution. I could save some brain power for the innovative part > or > >> > drink more beer watching the soccer world cup. At the same moment, I > >> > wonder why anyone in the python world would go through the hassle of > >> > using relational databases unless forced. > >> > > >> > So, has anyone experience with ZopeDB? Are there some drawbacks I > should > >> > > >> > be aware of before getting a book and dive in? (It sounds too good > ;-)) > >> > > >> > >> Jan - > >> > >> If you are evaluating alternative solutions, you might also look > >> into Django models. There have been some very positive comments > >> about Django on this list. And, Django models can be used outside > >> of the Django Web applications. Also, Django models are reasonably > >> object oriented. A Django model/DB can sit on top of several > >> different relational database engines, for example, PostgreSQL, MySQL, > >> sqlite3, etc. > >> > >> See: > >> > >> http://docs.djangoproject.com/en/1.2/#the-model-layer > >> http://www.djangobook.com/en/2.0/chapter05/ > >> > >> - Dave > >> > >> -- > >> Dave Kuhlman > >> http://www.rexx.com/~dkuhlman > >> _______________________________________________ > >> Tutor maillist - Tutor at python.org > >> To unsubscribe or change subscription options: > >> http://mail.python.org/mailman/listinfo/tutor > > > > _________________________________________________________________ > > Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. > > https://signup.live.com/signup.aspx?id=60969 > > > -- > Have a great day, > Alex (msg sent from GMail website) > mehgcap at gmail.com; http://www.facebook.com/mehgcap > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > Eldon; Same here in Mexico, in my hometown Guadalajara I couldn't find any Python course everything is either PHP, Delphi, Visual Basic or Java; I chose Java as a way of learning Python, sounds odd but since I don't have any programming background I was lacking the basics concepts and my self-teaching techniques were not doing a very good job; Java is HARD is confusing and most of my effort has gone into trying to memorize the steps in order to run a simple program; my idea is after this course I will re-take Python and understand it much better and of course as a Ihave already realized and actually miss its simplicity and beauty; so I guess it's true to say that "The more I learn Java the more I Love Python". -- ?Saludos! / Greetings! Juan Jos? Del Toro M. jdeltoro1973 at gmail.com Guadalajara, Jalisco MEXICO -------------- next part -------------- An HTML attachment was scrubbed... URL: From waynejwerner at gmail.com Sat Jun 12 20:22:03 2010 From: waynejwerner at gmail.com (Wayne Werner) Date: Sat, 12 Jun 2010 13:22:03 -0500 Subject: [Tutor] Linux webcam libraries? Message-ID: Hi, I want to do something like this: http://www.kulturblog.com/2007/11/marshie-attacks-halloween-interactive-driveway-activity/ I want to be able to grab a webcam image via python. So I'm curious if anyone has had any experience/luck in this particular area and/or knows of any libraries I should take a look at. I know my webcam definitely works under linux because I can use the cheese program and see the image... Anyway, any information will be very welcome! Thanks, Wayne -------------- next part -------------- An HTML attachment was scrubbed... URL: From imsam100 at yahoo.co.in Sat Jun 12 20:29:19 2010 From: imsam100 at yahoo.co.in (saurabh agrawal) Date: Sat, 12 Jun 2010 23:59:19 +0530 (IST) Subject: [Tutor] Tutor Digest, Vol 76, Issue 31 In-Reply-To: Message-ID: <290351.88493.qm@web94616.mail.in2.yahoo.com> Hi, You can use method name count in list also for getting the repeats. #!/usr/bin/python li=[1,2,3,1,4,5,7,3,4,1] for i in range(len(li)): ??? print li[i], li.count(li[i]) cheers, Saurabh --- On Fri, 11/6/10, tutor-request at python.org wrote: From: tutor-request at python.org Subject: Tutor Digest, Vol 76, Issue 31 To: tutor at python.org Date: Friday, 11 June, 2010, 8:19 PM Send Tutor mailing list submissions to ??? tutor at python.org To subscribe or unsubscribe via the World Wide Web, visit ??? http://mail.python.org/mailman/listinfo/tutor or, via email, send a message with subject or body 'help' to ??? tutor-request at python.org You can reach the person managing the list at ??? tutor-owner at python.org When replying, please edit your Subject line so it is more specific than "Re: Contents of Tutor digest..." Today's Topics: ???1. Looking for duplicates within a list (Ken G.) ???2. Re: Looking for duplicates within a list (Alex Hall) ???3. Re: Looking for duplicates within a list (Ken G.) ???4. Re: Looking for duplicates within a list (Ken G.) ???5. Re: Looking for duplicates within a list (Sander Sweers) ???6. Re: Looking for duplicates within a list (Jose Amoreira) ---------------------------------------------------------------------- Message: 1 Date: Fri, 11 Jun 2010 09:57:34 -0400 From: "Ken G." To: tutor at python.org Subject: [Tutor] Looking for duplicates within a list Message-ID: <4C1240CE.7050807 at insightbb.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed I have been working on this problem for several days and I am not making any progress.? I have a group of 18 number, in ascending order, within a list.? They ranged from 1 to 39.? Some numbers are duplicated as much as three times or as few as none. I started with one list containing the numbers.? For example, they are listed as like below: a = [1, 2, 3, 3, 4] I started off with using a loop: ? ? for j in range (0, 5): ? ? x = a[0] # for example, 1 How would I compare '1' with 2, 3, 3, 4? Do I need another duplicated list such as b = a and compare a[0] with either b[0], b[1], b[2], b[3], b[4]? Or do I compare a[0] with a[1], a[2], a[3], a[4]? In any event, if a number is listed more than once, I would like to know how many times, such as 2 or 3 times.? For example, '3' is listed twice within a list. TIA, Ken ------------------------------ Message: 2 Date: Fri, 11 Jun 2010 10:20:20 -0400 From: Alex Hall To: "Ken G." Cc: tutor at python.org Subject: Re: [Tutor] Looking for duplicates within a list Message-ID: ??? Content-Type: text/plain; charset=ISO-8859-1 On 6/11/10, Ken G. wrote: > I have been working on this problem for several days and I am not making > any progress.? I have a group of 18 number, in ascending order, within a > list.? They ranged from 1 to 39.? Some numbers are duplicated as much as > three times or as few as none. FYI, Python's "set" data type will let you have a list and never have a repeat. I know that is not your goal now, but if you want to remove duplicates, it seems like a good choice. > > I started with one list containing the numbers.? For example, they are > listed as like below: > > a = [1, 2, 3, 3, 4] > > I started off with using a loop: > >? ???for j in range (0, 5): >? ???x = a[0] # for example, 1 > > How would I compare '1' with 2, 3, 3, 4? > > Do I need another duplicated list such as b = a and compare a[0] with > either b[0], b[1], b[2], b[3], b[4]? > > Or do I compare a[0] with a[1], a[2], a[3], a[4]? A couple points here. First, you will want to make life easier by saying range(0, len(a)) so that the loop will work no matter the size of a. Second, for comparing a list to itself, here is a rather inefficient, though simple, way: for i in range(0, len(a)): x=a[i] for j in range(0, len(a)): ? y=a[j] ? if(x==y and i!=j): #match since a[i]==a[j] and i and j are not the same index of a > > In any event, if a number is listed more than once, I would like to know > how many times, such as 2 or 3 times.? For example, '3' is listed twice > within a list. Do not quote me here, but I think sets may be able to tell you that as well. > > TIA, > > Ken > > > > > > > > > _______________________________________________ > Tutor maillist? -? Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > -- Have a great day, Alex (msg sent from GMail website) mehgcap at gmail.com; http://www.facebook.com/mehgcap ------------------------------ Message: 3 Date: Fri, 11 Jun 2010 10:31:58 -0400 From: "Ken G." To: vnbang2003 at yahoo.com, tutor at python.org Subject: Re: [Tutor] Looking for duplicates within a list Message-ID: <4C1248DE.6090508 at insightbb.com> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" vijay wrote: > Check out this code >? l= [1, 2, 3, 3, 4] >? d={} >? for item in l: >? ? ? d.setdefaut(item,0) >? ? ? d[item] +=1 > print d > {1: 1, 2: 1, 3: 2, 4: 1} > > > with regard's > vijay > > Thanks.? Very interesting concept. Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: ------------------------------ Message: 4 Date: Fri, 11 Jun 2010 10:40:58 -0400 From: "Ken G." To: Alex Hall Cc: tutor at python.org Subject: Re: [Tutor] Looking for duplicates within a list Message-ID: <4C124AFA.7030007 at insightbb.com> Content-Type: text/plain; charset="iso-8859-1"; Format="flowed" Alex Hall wrote: > On 6/11/10, Ken G. wrote: >??? >> I have been working on this problem for several days and I am not making >> any progress.? I have a group of 18 number, in ascending order, within a >> list.? They ranged from 1 to 39.? Some numbers are duplicated as much as >> three times or as few as none. >>? ??? > FYI, Python's "set" data type will let you have a list and never have > a repeat. I know that is not your goal now, but if you want to remove > duplicates, it seems like a good choice. >??? >> I started with one list containing the numbers.? For example, they are >> listed as like below: >> >> a = [1, 2, 3, 3, 4] >> >> I started off with using a loop: >> >>? ???for j in range (0, 5): >>? ???x = a[0] # for example, 1 >> >> How would I compare '1' with 2, 3, 3, 4? >> >> Do I need another duplicated list such as b = a and compare a[0] with >> either b[0], b[1], b[2], b[3], b[4]? >> >> Or do I compare a[0] with a[1], a[2], a[3], a[4]? >>? ??? > A couple points here. First, you will want to make life easier by > saying range(0, len(a)) so that the loop will work no matter the size > of a. > Second, for comparing a list to itself, here is a rather inefficient, > though simple, way: > > for i in range(0, len(a)): >? x=a[i] >? for j in range(0, len(a)): >???y=a[j] >???if(x==y and i!=j): #match since a[i]==a[j] and i and j are not the > same index of a >??? >> In any event, if a number is listed more than once, I would like to know >> how many times, such as 2 or 3 times.? For example, '3' is listed twice >> within a list. >>? ??? > Do not quote me here, but I think sets may be able to tell you that as well. >??? >> TIA, >> >> Ken >>? ??? Thank you for your contribution.? As seen here, I have much to learn. Ken -------------- next part -------------- An HTML attachment was scrubbed... URL: ------------------------------ Message: 5 Date: Fri, 11 Jun 2010 16:46:25 +0200 From: Sander Sweers To: "Ken G." Cc: tutor at python.org Subject: Re: [Tutor] Looking for duplicates within a list Message-ID: ??? Content-Type: text/plain; charset=UTF-8 On 11 June 2010 15:57, Ken G. wrote: > In any event, if a number is listed more than once, I would like to know how > many times, such as 2 or 3 times. ?For example, '3' is listed twice within a > list. If you do not have top keep the order of the number this will work. >>> a = [1, 2, 3, 3, 4] >>> counted = {} >>> for n in a: ??? if not n in counted: ??? ??? counted[n] = 1 ??? else: ??? ??? counted[n] += 1 >>> counted {1: 1, 2: 1, 3: 2, 4: 1} >>> for x, y in counted.items(): ??? if y > 1: ??? ??? print "Number %s was found %s times" % (x, y) ??? else: ??? ??? print "Number %s was found %s time" % (x, y) Number 1 was found 1 time Number 2 was found 1 time Number 3 was found 2 times Number 4 was found 1 time Greets Sander ------------------------------ Message: 6 Date: Fri, 11 Jun 2010 15:49:22 +0100 From: Jose Amoreira To: tutor at python.org Subject: Re: [Tutor] Looking for duplicates within a list Message-ID: <201006111549.22751.ljmamoreira at gmail.com> Content-Type: Text/Plain;? charset="iso-8859-1" On Friday, June 11, 2010 02:57:34 pm Ken G. wrote: > I have been working on this problem for several days and I am not making > any progress.? I have a group of 18 number, in ascending order, within a > list.? They ranged from 1 to 39.? Some numbers are duplicated as much as > three times or as few as none. > > I started with one list containing the numbers.? For example, they are > listed as like below: > > a = [1, 2, 3, 3, 4] > > I started off with using a loop: > >? ???for j in range (0, 5): >? ???x = a[0] # for example, 1 > > How would I compare '1' with 2, 3, 3, 4? > > Do I need another duplicated list such as b = a and compare a[0] with > either b[0], b[1], b[2], b[3], b[4]? > > Or do I compare a[0] with a[1], a[2], a[3], a[4]? > > In any event, if a number is listed more than once, I would like to know > how many times, such as 2 or 3 times.? For example, '3' is listed twice > within a list. > > TIA, > I would do it with a dictionary: def reps(lst): ??? dict = {} ??? for item in lst: ??? ??? if item in dict: ??? ??? ??? dict[item] += 1 ??? ??? else: ??? ??? ??? dict[item] = 1 ??? return dict This function returns a dictionary with of the number of times each value in the list is repeated. Even shorter using dict.setdefault: def reps(lst): ??? dict={} ??? for item in lst: ??? ??? dict[item] = dict.setdefault(item,0) + 1 ??? return dict For instance, if lst=[1,2,2,2,4,4,5], then reps(lst) returns {1: 1, 2: 3, 4: 2, 5: 1} Using the fact that the list is ordered, one can design a more efficient solution (go through the list; if this item is equal to the previous, then it is repeated, else, it is a new value). But you list is short enough for this direct approach to work. Hope this helps. Cheers, Jose ------------------------------ _______________________________________________ Tutor maillist? -? Tutor at python.org http://mail.python.org/mailman/listinfo/tutor End of Tutor Digest, Vol 76, Issue 31 ************************************* -------------- next part -------------- An HTML attachment was scrubbed... URL: From alan.gauld at btinternet.com Sat Jun 12 21:56:21 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sat, 12 Jun 2010 20:56:21 +0100 Subject: [Tutor] Python a substitute/alternative for PhP? References: <4C1291AB.40804@googlemail.com>, <20100611222744.GB56775@cutter.rexx.com> Message-ID: "Eldon Londe Mello Junior" wrote First, please don't hijack an existing thread, this message appears under a thread about Zope DB! Always post a new message to start a new thread. It will get more readers and not confuse readers using threaded mail/newsreaders. > However, I've been reading a lot about programming > languages and stuff in order to make the best choice > as I don't want to spend much time learning unnecessary > things I won't need in the future. I'm not sure what you think the "unnecessary things" are but programming languages come and go and as a professional programmers you can expect to have to learn at least a dozen before you are done, probably more like two dozen. So don't think you will pick a single language and never have to learn another. As a minimum you will probably need to know: a) A general purpose language - Java, python, C++, Visual Basic, etc... b) SQL c) Javascript d) An OS shell language(DOS batch/WSH or a Linux shell(bash/csh or Korn) Very few modern applications have less than those 4 language groups embedded within them somewhere. The minimum I've ever seen in a professional project is 3. The maximum was 12 - but it was a big project. > opensource-solutions professional programmer. Caveat: There is not a lot of money in that market. People use Opensource because they expect it to be cheap. That means they won't pay the programmer as much either... At lerast thats my experience. There is much more money to be had programming Oracle or DB2 apps than creating MySql apps... > beginners start with PhP and stick with it or go for JAVA > or MS proprietary languages. Actually, you can only > learn python on your own around here as no college > or private institutes offer python courses. Pyton didn't even exist when I started, but neither did Java or C++ or VB... And in twenty years time possibly none of these languages will be in vogue and we will all be using periwinkle gizzard or whatever the latest craze is called... > FINAL QUESTION> Is Python a substitute for PHP? It can do similar things but it does it differently, especially for the web. Although you can write standalone PHP programs it is usually used on the Web. Most serious webv developers combine Python with a web framework like Django or Pylons or whatever. Arguably Python + Framework is superior to PHP - but less widely supported on ISP servers. > I mean, can I start learning python by trying to do the > things I've learned with PHP? You can, but the web elements will be very different. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From alan.gauld at btinternet.com Sat Jun 12 22:03:23 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sat, 12 Jun 2010 21:03:23 +0100 Subject: [Tutor] New to Programming References: Message-ID: "Kaushal Shriyan" wrote > I am absolutely new to programming language. Dont have any > programming > experience. Can some one guide me please. is python a good start for > novice. Yes, it is one of the best languages for an absolute beginner. It may be all the language you ever need but even if you branch out to others the principles you learn in Python will translate easily. There are a bunch of tutorials for absiolute beginners listed on the Python web site (including mine) Try here (or follow my .sig): http://wiki.python.org/moin/BeginnersGuide/NonProgrammers -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From alan.gauld at btinternet.com Sat Jun 12 21:59:52 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sat, 12 Jun 2010 20:59:52 +0100 Subject: [Tutor] Better construct? (was no subject) References: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> <4C13A250.5020405@gmail.com> Message-ID: "bob gailer" wrote > You can collect functions in a sequence, then iterate over it. This > allows for easy expansion (when you decide to add another function). > > funcs = (dosomething(), dosomethingelse()) I suspect Bob meant to leave off the (). You would normally just use the function name. (Unless these are factory functions returning another function but I don't think that was the intent! :-) funcs = (doSomething, doSomethingElse) > for func in funcs: > getid() > func() HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From alan.gauld at btinternet.com Sat Jun 12 22:10:20 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sat, 12 Jun 2010 21:10:20 +0100 Subject: [Tutor] Adding line numbers to a Python Script References: Message-ID: "Sudip Bhattacharya" wrote > for line in fileinput.input(inplace = true)............(2) > line = line.rstrip()........................................(3) > num=fileinput.lineno()..................................(4) > print '%-40s #%2i' %(line,num).....................(5) > > Line (3) - Are we stripping the entire line of code first, inserting > the > code at the end (line (5)) and then placing it back at the same > place ? Fire up the python interpreter and type: >>> help("".strip) See if you understand what it says. If not come back here and ask again. Python's help fuinction is very powerful, learn to use it for fast answers. > Line (5) - What does the individual characters in the expression > "Print > '%-40s #%2i' %(line,num)" mean ? These are formatting characters. If you read the Simple Sequences topic in my tutor you will get some easier examples to try. Then read the Python documentation - search for format string... > - '-40s' : is this the space [what does "-40s" mean] that we are > creating post - which the line nos is inserted "#%2i" ? Again fitre up the Python interpreter and try it out. >>> "%-40s" % "Some string here" Now try again with a different number, Try missing out the minus sign. Can you see what the different bits do? Now go read the documentation again. Try some different data types. Experiment. Its the best way to really understand. > - What does '%2" mean ? - Is that 2 cursor spaces of width ? Close but again Read the docs, try it, experiment. See for yourself. >>> "%2i" % 7 HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From alan.gauld at btinternet.com Sat Jun 12 22:12:48 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sat, 12 Jun 2010 21:12:48 +0100 Subject: [Tutor] Tutor Digest, Vol 76, Issue 31 References: <290351.88493.qm@web94616.mail.in2.yahoo.com> Message-ID: Please do not send the entire digest when replying rto a single email. Use your editor to remove the redundant material. -------------------- "saurabh agrawal" wrote You can use method name count in list also for getting the repeats. #!/usr/bin/python li=[1,2,3,1,4,5,7,3,4,1] for i in range(len(li)): print li[i], li.count(li[i]) cheers, Saurabh --- On Fri, 11/6/10, tutor-request at python.org wrote: From: tutor-request at python.org Subject: Tutor Digest, Vol 76, Issue 31 To: tutor at python.org Date: Friday, 11 June, 2010, 8:19 PM ... From alan.gauld at btinternet.com Sat Jun 12 22:17:37 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Sat, 12 Jun 2010 21:17:37 +0100 Subject: [Tutor] Problems with Importing into the Python Shell References: Message-ID: "Andrew Martin" wrote > am having some trouble. First off, I do not understand how to import > things > into the python shell. I have a script I saved as chap03.py, but > when I try > to import it into the python shell i get an error like this: > >>>> from chap03 import * > > Traceback (most recent call last): > File "", line 1, in > from chap03 import * > File "C:/Python26\chap03.py", line 2 > print param param > ^ > SyntaxError: invalid syntax OK, First things first. You have imported the file correctly. Thats why you are getting the error. Now read the error. It says there is a syntax error, which there is. Can you see what you have done wrong in the print statement. The little caret symbol is giving you a big clue... Finally, its considered bad style to use from foo import * It can lerad to difficult to debug problems where two files have things with the same name. It is better to use import foo and then use foo.name to access things. It is more typing but much safer and more reliable. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From bgailer at gmail.com Sun Jun 13 00:10:58 2010 From: bgailer at gmail.com (bob gailer) Date: Sat, 12 Jun 2010 18:10:58 -0400 Subject: [Tutor] Better construct? (was no subject) In-Reply-To: References: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> <4C13A250.5020405@gmail.com> Message-ID: <4C1405F2.5060506@gmail.com> On 6/12/2010 3:59 PM, Alan Gauld wrote: > > "bob gailer" wrote > >> You can collect functions in a sequence, then iterate over it. This >> allows for easy expansion (when you decide to add another function). >> >> funcs = (dosomething(), dosomethingelse()) > > I suspect Bob meant to leave off the (). Yep. Thank you for the correction. -- Bob Gailer 919-636-4239 Chapel Hill NC From eike.welk at gmx.net Sun Jun 13 01:27:42 2010 From: eike.welk at gmx.net (Eike Welk) Date: Sun, 13 Jun 2010 01:27:42 +0200 Subject: [Tutor] OT: Great find! In-Reply-To: References: Message-ID: <201006130127.42852.eike.welk@gmx.net> On Saturday June 12 2010 20:22:03 Wayne Werner wrote: > I want to do something like this: > http://www.kulturblog.com/2007/11/marshie-attacks-halloween-interactive-dri > veway-activity/ Great find! That's a very nice idea! Eike. From eldonjr at hotmail.com Sun Jun 13 02:58:17 2010 From: eldonjr at hotmail.com (Eldon Londe Mello Junior) Date: Sat, 12 Jun 2010 21:58:17 -0300 Subject: [Tutor] Python a substitute/alternative for PhP? In-Reply-To: References: <4C1291AB.40804@googlemail.com>, , <20100611222744.GB56775@cutter.rexx.com>, , Message-ID: Hi there, Just would like to thanks all of those who provided me with some insight about which ways to go about programming. I'll consider every single piece of advice. I would also like to apologize for I didn't mean to hijack no thread, that was just so stupid of me. As I'm finishing my PhP course by Monday now I feel comfortable enough to delve into Python which means you'll probably be hearing from me soon, Cheers for the English speakers and saludos a Jos? Del Toro! Eldon. _________________________________________________________________ Your E-mail and More On-the-Go. Get Windows Live Hotmail Free. https://signup.live.com/signup.aspx?id=60969 -------------- next part -------------- An HTML attachment was scrubbed... URL: From rabidpoobear at gmail.com Sun Jun 13 04:57:30 2010 From: rabidpoobear at gmail.com (Luke Paireepinart) Date: Sat, 12 Jun 2010 21:57:30 -0500 Subject: [Tutor] Better construct? (was no subject) In-Reply-To: <4C13A250.5020405@gmail.com> References: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> <4C13A250.5020405@gmail.com> Message-ID: > >> ## Can someone suggest a pythonesque way of doing this? >> >> >> def getid(): >> ? ?response ?= raw_input('prompt') >> ? ?if response not in [ "", "y", "Y", "yes"] : >> ? ? ? ?getid() ? ?# ouch >> ? ?print "continue working" >> ? ?# do more stuff >> ? ?# do more stuff >> This seems like really strange behavior. If the response is wrong, you will then have another instance of getid, then if they get the response correct, you will execute your code twice! Was that really your intent? I think what you really want is: def getid(): valid = False while not valid: response = raw_input('prompt') valid = response.strip().lower() in ["", "y", "yes"] >One improvement - response.lower().startswith("yes") will cover all your cases. Am I misunderstanding? They appear to have different behaviors. >>> x = "" >>> y = ["", "y", "Y", "yes"] >>> x not in y False >>> x.lower().startswith('yes') False >>> x = "yes" >>> x not in y False >>> x.lower().startswith('yes') True From steve at pearwood.info Sun Jun 13 05:03:32 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Sun, 13 Jun 2010 13:03:32 +1000 Subject: [Tutor] lib2to3 fixers In-Reply-To: References: Message-ID: <201006131303.33042.steve@pearwood.info> On Sat, 12 Jun 2010 05:27:39 am Zubin Mithra wrote: > Hey everyone, > > I just discovered that the following construct does not work in Py3k. > > >>> string.maketrans('-', '_') Like the error message says, you have to use bytes, which I grant is counter-intuitive, but it does work: >>> table = string.maketrans(b'-', b'_') >>> 'abc-def'.translate(table) 'abc_def' (Perhaps it shouldn't though... it seems to be an undocumented feature.) > However, the following works, > > >>> str.maketrans('-', '_') > > When i try to convert a python module containing the above construct, > it does not get modified in a way such that it could run on Python > 3.0 I think this should be reported as a bug/feature request on the bug tracker. Having 2to3 be as extensive as possible is a high priority to the Python development team. http://bugs.python.org/ > 1. replace string.maketrans() with a function which is compatible in > both Python 2.x and 3.0 ; as of now I`m unaware of such a construct. That at least is easy. def maketrans(a, b): try: return string.translate(a, b) except TypeError: return str.translate(a, b) > 2. write a fixer for doing this which I could use. I could`nt find > any good tutorials out there on writing fixers, i`d be grateful if > you could point me to any. For that you probably need to ask on the main Python mailing list or newsgroup: comp.lang.python http://mail.python.org/mailman/listinfo/python-list -- Steven D'Aprano From lie.1296 at gmail.com Sun Jun 13 10:08:29 2010 From: lie.1296 at gmail.com (Lie Ryan) Date: Sun, 13 Jun 2010 18:08:29 +1000 Subject: [Tutor] Linux webcam libraries? In-Reply-To: References: Message-ID: On 06/13/10 04:22, Wayne Werner wrote: > Hi, > > I want to do something like this: > http://www.kulturblog.com/2007/11/marshie-attacks-halloween-interactive-driveway-activity/ > > I want to be able to grab a webcam image via python. So I'm curious if > anyone has had any experience/luck in this particular area and/or knows of > any libraries I should take a look at. I know my webcam definitely works > under linux because I can use the cheese program and see the image... > I think the upcoming pygame2 will have a camera module, though I've never personally used it. From sander.sweers at gmail.com Sun Jun 13 11:35:02 2010 From: sander.sweers at gmail.com (Sander Sweers) Date: Sun, 13 Jun 2010 11:35:02 +0200 Subject: [Tutor] Linux webcam libraries? In-Reply-To: References: Message-ID: On 12 June 2010 20:22, Wayne Werner wrote: > I want to be able to grab a webcam image via python. So I'm curious if > anyone has had any experience/luck in this particular area and/or knows of > any libraries I should take a look at. I know my webcam definitely works > under linux because I can use the cheese program and see the image... Everything that captures video under linux is managed by video4linux [1]. You will have to figure out how to use it with python. A quick google search led me to v4l2capture [2]. Greets Sander [1] http://www.linuxtv.org/wiki/index.php/Main_Page [2] http://pypi.python.org/pypi/v4l2capture/1.2 From steve at pearwood.info Sun Jun 13 12:55:58 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Sun, 13 Jun 2010 20:55:58 +1000 Subject: [Tutor] (no subject) In-Reply-To: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> References: <6F3DC60E-3EE2-48B8-9C90-403BEC5FD784@robbstucky.net> Message-ID: <201006132055.59040.steve@pearwood.info> On Sat, 12 Jun 2010 07:12:27 am Advertising Department wrote: > #!/Library/Frameworks/Python.framework/Versions/Current/bin/pythonw > """still thinking in imperative" > """ There is absolutely nothing wrong with writing imperative code. Python makes it easy to mix imperative, functional and object-oriented code in the same application, and in truth you'll soon find that they blend into each other so easily that sometimes it's hard to tell the difference. > ## obviously this is a bad construct. > ## Can someone suggest a pythonesque way of doing this? You have to explain what you are aiming to do. > def getid(): > response = raw_input('prompt') > if response not in [ "", "y", "Y", "yes"] : > getid() # ouch > print "continue working" > # do more stuff > # do more stuff You have comments "do more stuff" (repeated twice, so I suppose that means there is a LOT of more stuff) in a function called "getid". *That* is a bad programming construct, and not just in Python, and not because it is imperative. It is because the getid() function should do ONE THING -- get the id, and nothing else. You should separate the *user interface* from the *backend* (the engine). So you should have two functions: def getid(): """Return the id.""" return 123456789 # FIXME everybody has the same id... def ask_id(prompt): prompt = prompt + ' (Y/n) ' done = False while not done: response = raw_input(prompt) done = response.lower() in ["", "y", "yes", "n", "no"] return response.lower() in ["", "y", "yes"] And then put them together in your main program like this: def main(): if ask_id('Would you like an ID?'): x = getid() do_something_with_id(x) print "Continue working"... do_some_work() do_some_more_work() while ask_id('Would you like another ID?'): x = getid() do_something_else_with_id(x) print "Done now!" main() Hope this helps. -- Steven D'Aprano From kaushalshriyan at gmail.com Sun Jun 13 17:38:27 2010 From: kaushalshriyan at gmail.com (Kaushal Shriyan) Date: Sun, 13 Jun 2010 21:08:27 +0530 Subject: [Tutor] New to Programming In-Reply-To: <4C1362B7.6070702@ieee.org> References: <4C1362B7.6070702@ieee.org> Message-ID: On Sat, Jun 12, 2010 at 4:04 PM, Dave Angel wrote: > Kaushal Shriyan wrote: >> >> Hi, >> >> I am absolutely new to programming language. Dont have any programming >> experience. Can some one guide me please. is python a good start for >> novice. >> >> Thanks, >> >> Kaushal >> >> > > Like nearly all questions, the answer is "it depends." > > Mainly, it depends on what your goal is. ?In my case, I made my living with > programming, for many years. ?And in the process, learned and used about 35 > languages, plus a few more for fun. ?I wish I had discovered Python much > earlier, though it couldn't have been my first, since it wasn't around. ?But > it'd have been much better than Fortran was, for learning. > > So tell us about your goals. ?Abstract knowledge, console utilities, gui > development, games, web development, networking communication, ... > > Next, you might want to evaluate what you already know. ?There are a lot of > non-programming things that a programmer needs to understand. ?If you > already know many of them, that's a big head start. ?If you already know how > to administer a Linux system, you're already a programmer and didn't know > it. ?If you write complex formulas for Excel, you're a programmer. ?If you > already know modus ponens, and understand what a contrapositive is, you've > got a head start towards logic (neither is a programming subject, just a > start towards logical thinking). ?If you've worked on a large document, and > kept backups of ?incremental versions, so you could rework the current > version based on earlier ones, that's a plus. ?If you know why a file's > timestamp might change when you copy it from hard disk to a USB drive and > back again, you've got a head start. ?If you know why it might have a > different timestamp when you look at it six months from now without changing > it, you've got a head start. > > If you're using Windows and never used a command prompt, you have a ways to > go. ?If you don't know what a file really is, or how directories are > organized, you have a ways to go. ?And if you think a computer is > intelligent, you have a long way to go. > > Python is a powerful tool. ?But if you're totally new to programming, it can > also be daunting. ?And most people have no idea how easy some programs are, > nor how hard some other programs are, to build. > > In any case, some of the things recommending Python as a first language are: > ?1) an interactive interpreter - you can experiment, trivially > ?2) very fast turnaround, from the time you make a change, till you can see > how it works. ?This can be true even for large programs > ?3) this mailing list > > DaveA > > Thanks Dave. You saved my day and really motivated me Kaushal From kaushalshriyan at gmail.com Sun Jun 13 17:38:38 2010 From: kaushalshriyan at gmail.com (Kaushal Shriyan) Date: Sun, 13 Jun 2010 21:08:38 +0530 Subject: [Tutor] New to Programming In-Reply-To: References: Message-ID: On Sun, Jun 13, 2010 at 1:33 AM, Alan Gauld wrote: > > "Kaushal Shriyan" wrote > >> I am absolutely new to programming language. Dont have any programming >> experience. Can some one guide me please. is python a good start for >> novice. > > Yes, it is one of the best languages for an absolute beginner. > It may be all the language you ever need but even if you branch > out to others the principles you learn in Python will translate easily. > > There are a bunch of tutorials for absiolute beginners listed > on the Python web site (including mine) > > Try here (or follow my .sig): > > http://wiki.python.org/moin/BeginnersGuide/NonProgrammers > > > -- > Alan Gauld > Author of the Learn to Program web site > http://www.alan-g.me.uk/ > Thanks Alan for the motivation. Kaushal From ilhs_hs at yahoo.com Sun Jun 13 23:45:45 2010 From: ilhs_hs at yahoo.com (Hs Hs) Date: Sun, 13 Jun 2010 14:45:45 -0700 (PDT) Subject: [Tutor] large file Message-ID: <461181.1334.qm@web111209.mail.gq1.yahoo.com> hi: I have a very large file 15Gb. Starting from 15th line this file shows the following lines: HWUSI-EAS1211_0001:1:1:977:20764#0 HWUSI-EAS1211_0001:1:1:977:20764#0 HWUSI-EAS1521_0001:1:1:978:13435#0 HWUSI-EAS1521_0001:1:1:978:13435#0 Every two lines are part of one readgroup. I want to add two variables to every line. First variable goes to all lines with odd numbers. Second variable should be appended to all even number lines. like the following: HWUSI-EAS1211_0001:1:1:977:20764#0 RG:Z:2301 HWUSI-EAS1211_0001:1:1:977:20764#0 RG:Z:2302 HWUSI-EAS1521_0001:1:1:978:13435#0 RG:Z:2301 HWUSI-EAS1521_0001:1:1:978:13435#0 RG:Z:2302 Since I cannot read the entire file, I wanted to cat the file something like this: cat myfile | python myscript.py > myfile.sam I do not know how to execute my logic after I read the line, althought I tried: myscript.py: while True: second = raw_input() x = second.split('\t') Could someone help me here either what I want to do. Or suggesting a different method. thanks -------------- next part -------------- An HTML attachment was scrubbed... URL: From bgailer at gmail.com Mon Jun 14 00:42:01 2010 From: bgailer at gmail.com (bob gailer) Date: Sun, 13 Jun 2010 18:42:01 -0400 Subject: [Tutor] large file In-Reply-To: <461181.1334.qm@web111209.mail.gq1.yahoo.com> References: <461181.1334.qm@web111209.mail.gq1.yahoo.com> Message-ID: <4C155EB9.1060200@gmail.com> On 6/13/2010 5:45 PM, Hs Hs wrote: > hi: > > I have a very large file 15Gb. Starting from 15th line this file shows > the following lines: > > HWUSI-EAS1211_0001:1:1:977:20764#0 > > HWUSI-EAS1211_0001:1:1:977:20764#0 > > HWUSI-EAS1521_0001:1:1:978:13435#0 > > HWUSI-EAS1521_0001:1:1:978:13435#0 > > > Every two lines are part of one readgroup. I want to add two variables > to every line. First variable goes to all lines with odd numbers. > Second variable should be appended to all even number lines. like the > following: > > HWUSI-EAS1211_0001:1:1:977:20764#0 RG:Z:2301 > > HWUSI-EAS1211_0001:1:1:977:20764#0 RG:Z:2302 > > HWUSI-EAS1521_0001:1:1:978:13435#0 RG:Z:2301 > > HWUSI-EAS1521_0001:1:1:978:13435#0 RG:Z:2302 > > Since I cannot read the entire file, I wanted to cat the file > > something like this: > > cat myfile | python myscript.py > myfile.sam > > > I do not know how to execute my logic after I read the line, althought > I tried: > > myscript.py: > > while True: > second = raw_input() > x = second.split('\t') > > # do something with first 14 lines? while True: line = raw_input().rstrip() if not line: break print line + " RG:Z:2301" line = raw_input().rstrip() if not line: break print line + " RG:Z:2302" -- Bob Gailer 919-636-4239 Chapel Hill NC -------------- next part -------------- An HTML attachment was scrubbed... URL: From alan.gauld at btinternet.com Mon Jun 14 02:19:21 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Mon, 14 Jun 2010 01:19:21 +0100 Subject: [Tutor] large file References: <461181.1334.qm@web111209.mail.gq1.yahoo.com> Message-ID: "Hs Hs" wrote > I have a very large file 15Gb. > Every two lines are part of one readgroup. > I want to add two variables to every line. > HWUSI-EAS1211_0001:1:1:977:20764#0 RG:Z:2301 > HWUSI-EAS1211_0001:1:1:977:20764#0 RG:Z:2302 > ... > Since I cannot read the entire file, I wanted to cat the file What makes you think you cannot read the entire file? > something like this: > > cat myfile | python myscript.py > myfile.sam How does that help over Python reading the file line by line? > I do not know how to execute my logic after I read the line, > althought I tried: > while True: > second = raw_input() > x = second.split('\t') Why are you splitting theline? You only need to append data to the end of the line... > Could someone help me here either what I want to do. In pseudo code: open input and ouput files read the first 14 lines from input oddLine = True while True: read line from input if oddLine: append odd data else append evenData write line to output file oddLine = not oddLine You probably want a try/except in there to catch the end of file. This is not very different from the menu example in the file handling topic of my tutorial... HTH -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From steve at pearwood.info Mon Jun 14 03:08:36 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Mon, 14 Jun 2010 11:08:36 +1000 Subject: [Tutor] large file In-Reply-To: <461181.1334.qm@web111209.mail.gq1.yahoo.com> References: <461181.1334.qm@web111209.mail.gq1.yahoo.com> Message-ID: <201006141108.36575.steve@pearwood.info> On Mon, 14 Jun 2010 07:45:45 am Hs Hs wrote: > hi: > > I have a very large file 15Gb. Starting from 15th line this file > shows the following lines: > > HWUSI-EAS1211_0001:1:1:977:20764#0 > HWUSI-EAS1211_0001:1:1:977:20764#0 > HWUSI-EAS1521_0001:1:1:978:13435#0 > HWUSI-EAS1521_0001:1:1:978:13435#0 It looks to me that your file has a *lot* of redundant information. Does the first part of the line "HWUSI-EAS1211_0001:1:1:" ever change? If it does not, then you can save approximately 65% of the file size by just recording it once, instead of 400 million times: [first 14 lines] prefix = HWUSI-EAS1211_0001:1:1: 977:20764#0 977:20764#0 978:13435#0 978:13435#0 [...] That will bring the file down from 15GB to less than 6GB, and speed up processing time and decrease storage requirements significantly. > Every two lines are part of one readgroup. I want to add two > variables to every line. First variable goes to all lines with odd > numbers. Second variable should be appended to all even number lines. How are these variables calculated? You need some way of automatically calculating them, perhaps by looking them up in a database. I don't know how you calculate them, so I will invent two simple stubs: def suffix1(line): # Calculate the first suffix variable. return " RG:Z:2301" def suffix2(line): # Calculate the first suffix variable. return " RG:Z:2302" > Since I cannot read the entire file, I wanted to cat the file Of course you can read the file, you just can't read it ALL AT ONCE. There's no need to use cat, you just have to read the file line by line and then do something with each line. infile = open("myfile", "r") outfile = open("output.sam", "w") # Skip over the first 15 lines. for i in range(15): infile.next() # Read one line. suffixes = [suffix1, suffix2] # Store the function objects. n = 0 # Process the lines. for line in infile: line = line.strip() # Which suffix function do we want to call? suffix = suffixes[n] outfile.write(line + suffix(line) + '\n') n = 1 - n # n -> 1, 0, 1, 0, 1, 0, ... outfile.close() infile.close() -- Steven D'Aprano From cristetoespiritante at gmail.com Mon Jun 14 13:06:54 2010 From: cristetoespiritante at gmail.com (cristeto1981) Date: Mon, 14 Jun 2010 04:06:54 -0700 (PDT) Subject: [Tutor] New to Programming In-Reply-To: <4C1362B7.6070702@ieee.org> References: <4C1362B7.6070702@ieee.org> Message-ID: <28878181.post@talk.nabble.com> Dave Angel wrote: > > Kaushal Shriyan wrote: >> Hi, >> >> I am absolutely new to programming language. Dont have any programming >> experience. Can some one guide me please. is python a good start for >> novice. >> >> Thanks, >> >> Kaushal >> >> > Like nearly all questions, the answer is "it depends." > > Mainly, it depends on what your goal is. In my case, I made my living > with programming, for many years. And in the process, learned and used > about 35 languages, plus a few more for fun. I wish I had discovered > Python much earlier, though it couldn't have been my first, since it > wasn't around. But it'd have been much better than Fortran was, for > learning. > > So tell us about your goals. Abstract knowledge, console utilities, gui > development, games, web development, networking communication, ... > > Next, you might want to evaluate what you already know. There are a lot > of non-programming things that a programmer needs to understand. If you > already know many of them, that's a big head start. If you already know > how to administer a Linux system, you're already a programmer and didn't > know it. If you write complex formulas for Excel, you're a programmer. > If you already know modus ponens, and understand what a contrapositive > is, you've got a head start towards logic (neither is a programming > subject, just a start towards logical thinking). If you've worked on a > large document, and kept backups of incremental versions, so you could > rework the current version based on earlier ones, that's a plus. If you > know why a file's timestamp might change when you copy it from hard disk > to a USB drive and back again, you've got a head start. If you know why > it might have a different timestamp when you look at it six months from > now without changing it, you've got a head start. > > If you're using Windows and never used a command prompt, you have a ways > to go. If you don't know what a file really is, or how directories are > organized, you have a ways to go. And if you think a computer is > intelligent, you have a long way to go. > > Python is a powerful tool. But if you're totally new to programming, it > can also be daunting. And most people have no idea how easy some > programs are, nor how hard some other programs are, to build. > > In any case, some of the things recommending Python as a first language > are: > 1) an interactive interpreter - you can experiment, trivially > 2) very fast turnaround, from the time you make a change, till you > can see how it works. This can be true even for large programs > 3) this mailing list > > DaveA > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > Thanks for this thread. It really helps. Those links were very informative. :) ----- [url=http://crosspromotion.wizard4u.com/]joint ventures[/url] -- View this message in context: http://old.nabble.com/-Tutor--New-to-Programming-tp28863541p28878181.html Sent from the Python - tutor mailing list archive at Nabble.com. From cristetoespiritante at gmail.com Mon Jun 14 13:08:13 2010 From: cristetoespiritante at gmail.com (cristeto1981) Date: Mon, 14 Jun 2010 04:08:13 -0700 (PDT) Subject: [Tutor] large file In-Reply-To: References: <461181.1334.qm@web111209.mail.gq1.yahoo.com> Message-ID: <28878191.post@talk.nabble.com> Alan Gauld wrote: > > > "Hs Hs" wrote > >> I have a very large file 15Gb. > >> Every two lines are part of one readgroup. >> I want to add two variables to every line. > >> HWUSI-EAS1211_0001:1:1:977:20764#0 RG:Z:2301 >> HWUSI-EAS1211_0001:1:1:977:20764#0 RG:Z:2302 >> ... >> Since I cannot read the entire file, I wanted to cat the file > > What makes you think you cannot read the entire file? > >> something like this: >> >> cat myfile | python myscript.py > myfile.sam > > How does that help over Python reading the file line by line? > >> I do not know how to execute my logic after I read the line, >> althought I tried: > >> while True: >> second = raw_input() >> x = second.split('\t') > > Why are you splitting theline? You only need to append > data to the end of the line... > >> Could someone help me here either what I want to do. > > In pseudo code: > > open input and ouput files > read the first 14 lines from input > oddLine = True > while True: > read line from input > if oddLine: > append odd data > else > append evenData > write line to output file > oddLine = not oddLine > > You probably want a try/except in there to catch the end of file. > > > This is not very different from the menu example in the file > handling topic of my tutorial... > > HTH > > -- > Alan Gauld > Author of the Learn to Program web site > http://www.alan-g.me.uk/ > > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > Thanks for this thread. This is very helful. I'm learning a lot from you guys. :) ----- [url=http://crosspromotion.wizard4u.com/]joint ventures[/url] -- View this message in context: http://old.nabble.com/-Tutor--large-file-tp28874185p28878191.html Sent from the Python - tutor mailing list archive at Nabble.com. From advertising at robbstucky.net Mon Jun 14 21:06:01 2010 From: advertising at robbstucky.net (Advertising Department) Date: Mon, 14 Jun 2010 15:06:01 -0400 Subject: [Tutor] Better construct? Message-ID: Many thanks to all, repeat WHILE is exactly what I needed. I got BASIC stuck in my head. GOTO line# YUCK! From alan.gauld at btinternet.com Tue Jun 15 01:30:29 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Tue, 15 Jun 2010 00:30:29 +0100 Subject: [Tutor] Better construct? References: Message-ID: "Advertising Department" wrote > repeat WHILE > is exactly what I needed. > > I got BASIC stuck in my head. GOTO line# YUCK! BASIC has a WHILE/WEND construct too :-) Even GW Basic supported that. Alan G. From lang at tharin.com Tue Jun 15 02:08:38 2010 From: lang at tharin.com (Lang Hurst) Date: Mon, 14 Jun 2010 17:08:38 -0700 Subject: [Tutor] Structuring a class Message-ID: <4C16C486.70804@tharin.com> I'm trying to figure out how to deal with data which will look something like: Student:Bob Hurley ID: 123456 Period:4 Grad_class: 2012 Credits: Algebra C (20P) Chapter 1 Date: September 14, 2010 Grade: 87 Credits:1.5 Notes: Probably cheated on final. Really watch on next quiz/test. Chapter 2 Date: October 31, 2010 . . **and so on** . Consumer Math (24G) Module 2 . . **more information like above** . So, I just figured that I would have a couple of nested dictionaries. bob = Student('123456','Bob Hurley') bob.period = 4 bob.grad_class = 2010 bob['credits']['Algebra C (20P)']={'Chapter 1':{'Date':'September 12, 2010', 'Grade':'87', **and so on**}} This works, for the most part, from the command line. So I decided to set up a class and see if I could work it from that standpoint (I'm doing this to scratch an itch, and try to learn). My preliminary class looks like: class Student: def __init__(self, ident=' ', name=' ', period=' ', grad_class=' ', subject=' ', notes=' ', credit=' '): self.name = name self.ident = ident self.period = period self.notes = notes self.grad_class = grad_class # self.credit = {{}} <--- BAD self.credit = {} I'm sure that someone will enlighten me as to where my poor coding skills are especially weak. It's the last line there (self.credit...) which I can't figure out. The credits may be in any of about 30 different subjects (teaching at a continuation high school makes for interesting times). If I don't set it to anything, ie, like it is, I get an error Stud instance has no attribute '__getitem__' If I try to leave it available for adding to somewhat dynamically, I get a 'wtf' from python. Sorry for the novel, I'm just wondering if someone would set me straight. Should I even use a class? If so, how do I set up a class item which let's me add dictionaries to it? Thanks. -Lang -- There are no stupid questions, just stupid people. From bgailer at gmail.com Tue Jun 15 05:13:00 2010 From: bgailer at gmail.com (bob gailer) Date: Mon, 14 Jun 2010 23:13:00 -0400 Subject: [Tutor] Structuring a class In-Reply-To: <4C16C486.70804@tharin.com> References: <4C16C486.70804@tharin.com> Message-ID: <4C16EFBC.6080907@gmail.com> On 6/14/2010 8:08 PM, Lang Hurst wrote: > I'm trying to figure out how to deal with data which will look > something like: > > Student:Bob Hurley > ID: 123456 > Period:4 > Grad_class: 2012 > Credits: > Algebra C (20P) > Chapter 1 > Date: September 14, 2010 > Grade: 87 > Credits:1.5 > Notes: Probably cheated on final. Really watch on > next quiz/test. > Chapter 2 > Date: October 31, 2010 > . > . **and so on** > . > Consumer Math (24G) > Module 2 > . > . **more information like above** > . > Before deciding on data structures I suggest you give the big picture. Where will data come from? What do you plan to do with it? Often a case like this is better handled using a relational database. Python happens to come with the sqlite3 module which makes database work quite easy. > > So, I just figured that I would have a couple of nested dictionaries. > > bob = Student('123456','Bob Hurley') > bob.period = 4 > bob.grad_class = 2010 > bob['credits']['Algebra C (20P)']={'Chapter 1':{'Date':'September > 12, 2010', 'Grade':'87', **and so on**}} > > This works, for the most part, from the command line. So I decided to > set up a class and see if I could work it from that standpoint (I'm > doing this to scratch an itch, and try to learn). My preliminary > class looks like: > > class Student: > def __init__(self, ident=' ', name=' ', period=' ', > grad_class=' ', subject=' ', notes=' ', credit=' '): > self.name = name > self.ident = ident > self.period = period > self.notes = notes > self.grad_class = grad_class > # self.credit = {{}} <--- BAD > self.credit = {} > > I'm sure that someone will enlighten me as to where my poor coding > skills are especially weak. It's the last line there (self.credit...) > which I can't figure out. The credits may be in any of about 30 > different subjects (teaching at a continuation high school makes for > interesting times). You should define a class for Credit, which will hold the credit attributes, just like you did for Student. Then assign instances of Credit to entries in self.credit. > > If I don't set it to anything, ie, like it is, I get an error > > Stud instance has no attribute '__getitem__' > > If I try to leave it available for adding to somewhat dynamically, I > get a 'wtf' from python. Sorry I don't understand these. It is a good idea to post full tracebacks and the code that raises the exception. -- Bob Gailer 919-636-4239 Chapel Hill NC From lang at tharin.com Tue Jun 15 06:01:31 2010 From: lang at tharin.com (Lang Hurst) Date: Mon, 14 Jun 2010 21:01:31 -0700 Subject: [Tutor] Structuring a class In-Reply-To: <4C16EFBC.6080907@gmail.com> References: <4C16C486.70804@tharin.com> <4C16EFBC.6080907@gmail.com> Message-ID: <4C16FB1B.30405@tharin.com> bob gailer wrote: > > Often a case like this is better handled using a relational database. > Python happens to come with the sqlite3 module which makes database > work quite easy. > > > You should define a class for Credit, which will hold the credit > attributes, just like you did for Student. Then assign instances of > Credit to entries in self.credit. >> Last time I did anything with python, it was years ago on a web application and I ended up using gadfly as a database. I did not know that sqlite3 came as a module for python. That just made it much, much easier. I've done much more work with databases. Thank you. I figured that I was probably missing something obvious. -Lang -- There are no stupid questions, just stupid people. From eduardo.susan at gmail.com Tue Jun 15 06:11:59 2010 From: eduardo.susan at gmail.com (Eduardo Vieira) Date: Mon, 14 Jun 2010 22:11:59 -0600 Subject: [Tutor] large file In-Reply-To: <28878191.post@talk.nabble.com> References: <461181.1334.qm@web111209.mail.gq1.yahoo.com> <28878191.post@talk.nabble.com> Message-ID: > Thanks for this thread. This is very helful. I'm learning a lot from you > guys. :) > > ----- > [url=http://crosspromotion.wizard4u.com/]joint ventures[/url] > > -- > View this message in context: http://old.nabble.com/-Tutor--large-file-tp28874185p28878191.html > Sent from the Python - tutor mailing list archive at Nabble.com. > > _______________________________________________ > Tutor maillist ?- ?Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > I think this subscriber is just spamming. Two post with the same text. Eduardo From hgfernan at gmail.com Tue Jun 15 02:36:57 2010 From: hgfernan at gmail.com (Hilton Fernandes) Date: Mon, 14 Jun 2010 21:36:57 -0300 Subject: [Tutor] Better construct? In-Reply-To: References: Message-ID: Alan, GW-Basic supported that, but it was not common programming use. :) I've learned programming using Algol (parent of Pascal) and people used to frown at my insistence in using WHILE/WEND Thanks, Hilton On Mon, Jun 14, 2010 at 8:30 PM, Alan Gauld wrote: > > "Advertising Department" wrote > >> ?repeat WHILE >> is exactly what I needed. >> >> I got BASIC stuck in my head. GOTO line# YUCK! > > BASIC has a WHILE/WEND construct too :-) > Even GW Basic supported that. > > Alan G. > > _______________________________________________ > Tutor maillist ?- ?Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > From alan.gauld at btinternet.com Tue Jun 15 09:44:15 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Tue, 15 Jun 2010 08:44:15 +0100 Subject: [Tutor] Structuring a class References: <4C16C486.70804@tharin.com> Message-ID: "Lang Hurst" wrote > I'm trying to figure out how to deal with data which will look > something like: > > Student:Bob Hurley > Credits: > Algebra C (20P) > Chapter 1 > Chapter 2 > Consumer Math (24G) > Module 2 > > So, I just figured that I would have a couple of nested > dictionaries. Or 3 classes: Student, Credit, Module But classses will be most useful if you are doing a lot of interaction between the students or calculations based on the credits. As Bob suggested, if you mainly just want to add/delete/modify and report on the data a database is a better bet. You mght still create a Student class to structure the data coming back from the database but the other classes will probably be overkill and your double dict will be as effective. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From pedrooconnell at gmail.com Tue Jun 15 14:27:43 2010 From: pedrooconnell at gmail.com (Pete O'Connell) Date: Tue, 15 Jun 2010 21:57:43 +0930 Subject: [Tutor] conventions for establishing and saving default values for variables Message-ID: Hi I was wondering if anyone could give me some insight as to the best way to get and save variables from a user the first time a script is opened. For example if the script prompts something like "What is the path to the folder?" and the result is held in a variable called thePath, what is the best way to have that variable saved for all subsequent uses of the script by the same user. Pete -------------- next part -------------- An HTML attachment was scrubbed... URL: From cwitts at compuscan.co.za Tue Jun 15 15:02:22 2010 From: cwitts at compuscan.co.za (Christian Witts) Date: Tue, 15 Jun 2010 15:02:22 +0200 Subject: [Tutor] conventions for establishing and saving default values for variables In-Reply-To: References: Message-ID: <4C1779DE.6070408@compuscan.co.za> Pete O'Connell wrote: > Hi I was wondering if anyone could give me some insight as to the best > way to get and save variables from a user the first time a script is > opened. For example if the script prompts something like "What is the > path to the folder?" and the result is held in a variable called > thePath, what is the best way to have that variable saved for all > subsequent uses of the script by the same user. > Pete > ------------------------------------------------------------------------ > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > ConfigParser can read/write config files or using Pickle/cPickle to save & load your variables or using something like JSON (JavaScript Object Notation) will do what you want. For something like just storing a path for future use using ConfigParser would be perfectly suited to the task. import ConfigParser cfg = ConfigParser.ConfigParser() cfg.read('options.cfg') if not cfg.sections(): work_path = raw_input('Please enter the workspace path: ') cfg.add_section('PATH') cfg.set('PATH', 'workspace', work_path) f = open('options.cfg', 'w') cfg.write(f) f.close() else: work_path = cfg.get('PATH', 'workspace') -- Kind Regards, Christian Witts From hugo.yoshi at gmail.com Tue Jun 15 15:04:55 2010 From: hugo.yoshi at gmail.com (Hugo Arts) Date: Tue, 15 Jun 2010 15:04:55 +0200 Subject: [Tutor] conventions for establishing and saving default values for variables In-Reply-To: References: Message-ID: On Tue, Jun 15, 2010 at 2:27 PM, Pete O'Connell wrote: > Hi I was wondering if anyone could give me some insight as to the best way > to get and save variables from a user the first time a script is opened. For > example if the script prompts something like "What is the path to the > folder?" and the result is held in a variable called thePath, what is the > best way to have that variable saved for all subsequent uses of the script > by the same user. > Pete In UNIX-likes, It would be a configuration file in their home directory, I suppose. Under windows, probably the registry. There's the _winreg and configparser modules. Hugo From steve at pearwood.info Tue Jun 15 15:40:38 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Tue, 15 Jun 2010 23:40:38 +1000 Subject: [Tutor] conventions for establishing and saving default values for variables In-Reply-To: References: Message-ID: <201006152340.38925.steve@pearwood.info> On Tue, 15 Jun 2010 10:27:43 pm Pete O'Connell wrote: > Hi I was wondering if anyone could give me some insight as to the > best way to get and save variables from a user the first time a > script is opened. For example if the script prompts something like > "What is the path to the folder?" and the result is held in a > variable called thePath, what is the best way to have that variable > saved for all subsequent uses of the script by the same user. Others have already mentioned ConfigParser. You should also check out plistlib, in the standard library since version 2.6. Other alternatives include pickle, XML, JSON or YAML (although since YAML is not part of the standard library, you will need to download a package for it). On Windows you can write to the registry, although since I'm not a Windows user I don't know how. Or if your config is simple enough, you can just write your data to the file manually. But honestly, you can't get much simpler than ConfigParser or plistlib. -- Steven D'Aprano From jeff at dcsoftware.com Tue Jun 15 17:18:54 2010 From: jeff at dcsoftware.com (Jeff Johnson) Date: Tue, 15 Jun 2010 08:18:54 -0700 Subject: [Tutor] conventions for establishing and saving default values for variables In-Reply-To: <201006152340.38925.steve@pearwood.info> References: <201006152340.38925.steve@pearwood.info> Message-ID: <4C1799DE.8000105@dcsoftware.com> Steven D'Aprano wrote: > On Tue, 15 Jun 2010 10:27:43 pm Pete O'Connell wrote: > >> Hi I was wondering if anyone could give me some insight as to the >> best way to get and save variables from a user the first time a >> script is opened. For example if the script prompts something like >> "What is the path to the folder?" and the result is held in a >> variable called thePath, what is the best way to have that variable >> saved for all subsequent uses of the script by the same user. >> > > Others have already mentioned ConfigParser. You should also check out > plistlib, in the standard library since version 2.6. > > Other alternatives include pickle, XML, JSON or YAML (although since > YAML is not part of the standard library, you will need to download a > package for it). On Windows you can write to the registry, although > since I'm not a Windows user I don't know how. Or if your config is > simple enough, you can just write your data to the file manually. But > honestly, you can't get much simpler than ConfigParser or plistlib. > > > > On Windows I create an ".ini" file in the user profile instead of the registry. Windows API has GetPrivateProfileString and WritePrivateProfileString. On Linux I use ConfigParser to read and write to an ".ini" file in the home directory. I have avoided the Windows registry completely. Obviously you could use ConfigParser on Windows because of Python. -- Jeff ------------------- Jeff Johnson jeff at dcsoftware.com -------------- next part -------------- An HTML attachment was scrubbed... URL: From juhasecke at googlemail.com Tue Jun 15 19:26:15 2010 From: juhasecke at googlemail.com (Jan Ulrich Hasecke) Date: Tue, 15 Jun 2010 19:26:15 +0200 Subject: [Tutor] What's the catch with ZopeDB? In-Reply-To: <4C1291AB.40804@googlemail.com> References: <4C1291AB.40804@googlemail.com> Message-ID: Am 11.06.10 21:42, schrieb Knacktus: > So, has anyone experience with ZopeDB? Are there some drawbacks I should > be aware of before getting a book and dive in? (It sounds too good ;-)) You can easily use the ZODB to create pure python applications. There are some tutorials around, like this one: http://www.zodb.org/documentation/tutorial.html Check out: http://www.zodb.org/ The Zope Community uses the ZODB for several mission critical applications like content management systems and other very huge web applications. There are no drawbacks I heard of, but it all depends on your usecase. juh From alan.gauld at btinternet.com Tue Jun 15 19:49:40 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Tue, 15 Jun 2010 18:49:40 +0100 Subject: [Tutor] conventions for establishing and saving default values forvariables References: Message-ID: "Pete O'Connell" wrote > Hi I was wondering if anyone could give me some insight as to the > best way > to get and save variables from a user the first time a script is > opened. For > example if the script prompts something like "What is the path to > the > folder?" and the result is held in a variable called thePath, what > is the > best way to have that variable saved for all subsequent uses of the > script > by the same user. Others have mentioned ini files on Windows and resource files in *nix as well as other options. Another option depending on the purpose might be an environment variable. But that would normally only be used to, for example, set a path to where the ini file was located - especially if it wasn't in the default location, maybe being shared by a user group, say. So it depends on the function of your variable too. Personally I'd go with an ini/resource file in the users home directory as being the most consistent and simplest solution. -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From hgfernan at gmail.com Tue Jun 15 20:17:31 2010 From: hgfernan at gmail.com (Hilton Fernandes) Date: Tue, 15 Jun 2010 15:17:31 -0300 Subject: [Tutor] Structuring a class In-Reply-To: References: <4C16C486.70804@tharin.com> Message-ID: inded, a relational database is the best bet here. however, a direct implementation in Python may need less previous knowledge. On Tue, Jun 15, 2010 at 4:44 AM, Alan Gauld wrote: > "Lang Hurst" wrote > >> I'm trying to figure out how to deal with data which will look something >> like: >> >> ? Student:Bob Hurley >> ? Credits: >> ? ? ?Algebra C (20P) >> ? ? ? ? ? ?Chapter 1 >> ? ? ? ? ? ?Chapter 2 >> ? ? ?Consumer Math (24G) >> ? ? ? ? ? ?Module 2 >> >> So, I just figured that I would have a couple of nested dictionaries. > > Or 3 classes: Student, Credit, Module > > But classses will be most useful if you are doing a lot of > interaction between the students or calculations based on the credits. > > As Bob suggested, if you mainly just want to add/delete/modify > and report on the data a database is a better bet. > > You mght still create a Student class to structure the data > coming back from the database but the other classes will > probably be overkill and your double dict will be as effective. > > HTH, > > -- > Alan Gauld > Author of the Learn to Program web site > http://www.alan-g.me.uk/ > > > _______________________________________________ > Tutor maillist ?- ?Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > From jf_byrnes at comcast.net Tue Jun 15 22:39:27 2010 From: jf_byrnes at comcast.net (Jim Byrnes) Date: Tue, 15 Jun 2010 15:39:27 -0500 Subject: [Tutor] Tkinter - master attribute In-Reply-To: References: <4C0E7204.6080908@comcast.net> Message-ID: <4C17E4FF.6020705@comcast.net> Alan Gauld wrote: > > "Jim Byrnes" wrote in > >> When reading code examples I see things like > >> theframe.master.title('spam) > >> def __init__(self, master): >> frame = Frame(master) > >> When I encounter these I tend to get bogged down trying to decide if >> "master" has special meaning or is just a name the author has chosen. > > In the first case master is an attribute of the frame and as > such is defined by the frame definition. > > In the second case master is just an arbitrary name for a > parameter like any other. Because it is being used to correspond > to the master attribute of the Framer(as seen in the call to Frame() ) > the author has used the name master too. But other common > names for the same attribute are parent, root, top, etc > >> For example is it similar to Buttton(text='spam) where text in this >> case has special meaning. > > In the first example yes, in the second no. > Although 'text' is even more special because it is actually defined in > the underlying Tk code rather than in Tkinter Python code. > >> I've goolged and found references to "widgets master attributes" but >> nothing to really explain it. Could someone point me to a good >> reference so that I could better understand it use. > > Because Tkinter is a thin wrapper around the underlying Tk tookit > many atttributes of widgets are actually defined in the Tk code > and simply mirrored by Tkinter. In that sense the widget attributes > tend to have fixed names. But in Tkinter code the naming is > essentially arbitrary and follows the usual Python naming > conventions. > > HTH, > Alan, Sorry it took so long for me to get back to this issue. Thanks to you and Steve for your replies. I still am having trouble understanding the use of "master" in Tkinter. I think the problem is I can't find any reference that explains the concept around master, like the Button example I gave above. If I want to put the word spam on a Button I found a reference that said you type the word text followed by an equal sign followed by spam in quotes. Let me try another example. The code snippet below comes from a working example out of a book: class CanvasEventsDemo(canvasDraw.CanvasEventsDemo): def __init__(self, parent=None): canvasDraw.CanvasEventsDemo.__init__(self, parent) self.canvas.create_text(75, 8, text='Press o and r to move shapes') self.canvas.master.bind('', self.onMoveOvals) self.canvas.master.bind('', self.onMoveRectangles) self.kinds = self.create_oval_tagged, self.create_rectangle_tagged The word master appears only twice in the entire script so it is not defined somewhere else in the script. As an experiment I changed them both to masterx. When I ran the script I got the following error: Traceback (most recent call last): File "canvasDraw_tags.py", line 41, in CanvasEventsDemo() File "canvasDraw_tags.py", line 16, in __init__ self.canvas.masterx.bind('', self.onMoveOvals) AttributeError: Canvas instance has no attribute 'masterx' So the Canvas does not have a masterx attribute but does have one called master. Maybe the bottom line question is where can I look to see a list of a widgets attributes? Sorry to be so dense about this but I just don't get it yet. Thanks, Jim From alan.gauld at btinternet.com Wed Jun 16 02:30:31 2010 From: alan.gauld at btinternet.com (ALAN GAULD) Date: Wed, 16 Jun 2010 00:30:31 +0000 (GMT) Subject: [Tutor] Tkinter - master attribute In-Reply-To: <4C17E4FF.6020705@comcast.net> References: <4C0E7204.6080908@comcast.net> <4C17E4FF.6020705@comcast.net> Message-ID: <428097.47271.qm@web86702.mail.ird.yahoo.com> > I still am having trouble understanding the use of "master" in > Tkinter. I think the problem is I can't find any reference that explains the > concept around master, If you read the GUI topic in my tutorial it explains the concept of a containment tree that is common to ost GUI frameworks including Tkinter. All widgets belong to a parent or master widget until you get to some kind of root or main window that is the master odf all its sub widgets. When you delete a window you delete the master and it deletes all its children. The children delete their children, and so on until all the widgets making up the window are deleted. Thats how GUIs work. Similarly if you add a widget to a window you must tell the new widget where within the containment tree it sits, you tell it who its master is. Usually the widget will register itself with its master. > put the word spam on a Button I found a reference that said you type the word > text followed by an equal sign followed by spam in quotes. That's slightly different in that text is an attribute of the widget itself. By assigning 'Spam' to the attribute you control the look of that particular Button widget. class CanvasEventsDemo(canvasDraw.CanvasEventsDemo): def __init__(self, parent=None): canvasDraw.CanvasEventsDemo.__init__(self, parent) Here parent is being used instead of master. Thats quite common. > self.canvas.master.bind('', self.onMoveOvals) Here the master attribute is being accessed. That is an attribute of the canvas widget. > word master appears only twice in the entire script so it is not defined > somewhere else in the script. It is an inherited attribute and is inherited by all widgets although from where is a little bit mysterious - see below... > AttributeError: Canvas instance has no attribute > 'masterx' > > So the Canvas does not have a masterx attribute but does have > one called master. Maybe the bottom line question is where can I look to > see a list of a widgets attributes? You can use dir() or help(). However in Tkinter it is further complicated by the mapping of Tkinter to the underlying Tk widgets. It is not always 1-1 and some attributes are implemented by the Tk tookit rather than at the Tkinter level and these do not always show up in dir(). Master appears to be one of these. However, on digging a little deeper it seems there is a subtle distinction in Tkinter between the containment hierarchy and the geometry manager hierarchy. I confess that I've never noticed this before and have only skimmed the material(Grayson's Tkinter book) but it seems that master refers to the GM hierarchy and parent to the containment one. In most cases they will be the same but they can be different. But because of this master seems to be implemented somewhere in the GM code rather than the widget code... In most cases you can ignore that - as I have been doing for the last 10 years! :-) Just use master as an inherited attribute that is present in all widgets. > Sorry to be so dense about this but I just don't get it yet. You are not being dense but asking rather deep questions which probably need someone who understands the Tkinter implementatioon to answer. You probably don't really need to know the detail, just accept that master will be the attribute and it will be there in each widget class you use. If I get the time I will try to track this down further now that you have piqued my curiosity. HTH, Alan G. From david.fockens at gmail.com Wed Jun 16 03:21:39 2010 From: david.fockens at gmail.com (David) Date: Tue, 15 Jun 2010 18:21:39 -0700 Subject: [Tutor] Passing arguments to CGI script Message-ID: <20100615182139.0593dd38@gmail.com> Hi, I'm trying to pass arguments to a python script running on my webserver. Here is the script: import cgi import cgitb import sys cgitb.enable() form = cgi.FieldStorage() title = form.getvalue("title") print """Content-type: text/html """ print form.keys() print """ """ When I run it on the website like http://mf-doom.com/album.py?title=blah it just prints out an empty array. Is there something wrong with my code? Or is there something wrong with the way my server's configured? From amonroe at columbus.rr.com Wed Jun 16 13:39:44 2010 From: amonroe at columbus.rr.com (R. Alan Monroe) Date: Wed, 16 Jun 2010 07:39:44 -0400 Subject: [Tutor] conventions for establishing and saving default values for variables In-Reply-To: References:

Message-ID: <193806680405.20100616073944@columbus.rr.com> > On Tue, Jun 15, 2010 at 2:27 PM, Pete O'Connell wrote: >> Hi I was wondering if anyone could give me some insight as to the best way >> to get and save variables from a user the first time a script is opened. For >> example if the script prompts something like "What is the path to the >> folder?" and the result is held in a variable called thePath, what is the >> best way to have that variable saved for all subsequent uses of the script >> by the same user. >> Pete > In UNIX-likes, It would be a configuration file in their home > directory, I suppose. Under windows, probably the registry. There's > the _winreg and configparser modules. Consider using the %USERPROFILE% environment variable rather than the registry. Alan From alan.gauld at btinternet.com Wed Jun 16 19:25:03 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Wed, 16 Jun 2010 18:25:03 +0100 Subject: [Tutor] conventions for establishing and saving default valuesfor variables References:

<193806680405.20100616073944@columbus.rr.com> Message-ID: "R. Alan Monroe" wrote >> directory, I suppose. Under windows, probably the registry. There's >> the _winreg and configparser modules. > > Consider using the %USERPROFILE% environment variable rather than > the > registry. How would that work? That is just a single variable that points to the users Settings folder. Effectively their home directory in unix terms, so you could store the config file there. But you couldn't store the kind of data you would store in the registry? I'm confused. -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From jeff at dcsoftware.com Wed Jun 16 19:44:58 2010 From: jeff at dcsoftware.com (Jeff Johnson) Date: Wed, 16 Jun 2010 10:44:58 -0700 Subject: [Tutor] conventions for establishing and saving default values for variables In-Reply-To: References: Message-ID: <4C190D9A.3010403@dcsoftware.com> Pete O'Connell wrote: > Hi I was wondering if anyone could give me some insight as to the best > way to get and save variables from a user the first time a script is > opened. For example if the script prompts something like "What is the > path to the folder?" and the result is held in a variable called > thePath, what is the best way to have that variable saved for all > subsequent uses of the script by the same user. > Pete > ------------------------------------------------------------------------ > > I will send you my python script that reads and writes to a windows style .ini file if you want me to. -- Jeff ------------------- Jeff Johnson jeff at dcsoftware.com -------------- next part -------------- An HTML attachment was scrubbed... URL: From knacktus at googlemail.com Wed Jun 16 22:39:44 2010 From: knacktus at googlemail.com (Knacktus) Date: Wed, 16 Jun 2010 22:39:44 +0200 Subject: [Tutor] How to model objects aimed to persistence? Message-ID: <4C193690.5070103@googlemail.com> Hi everyone, within a python application I can easily model object association with simple references, e.g.: ################################################################# class FavoritMovies(object): def __init__(self, movies): self.movies = movies class Movie(object): def __init__(self, name, actor): self.name = name self.actor = actor gladiator = Movie("Gladiator", "Russel Crowe") my_favorit_movies = FavoritMovies([gladiator]) kung_fu_panda = Movie("Kung Fu Panda", "Jack Black") your_favorit_movies = FavoritMovies([gladiator, kung_fu_panda]) ################################################################## So far, so good. But what is best practise to prepare this data for general persistence? It should be usable for serialisation to xml or storing to an RDBMS or ObjectDatabase ... I guess I have to incorporate some kind of id for every object and use this as reference with some kind of look-up dictionary, but I wouldn't like it and hope that there're some other sweet pythonic solutions? Cheers, Jan From breamoreboy at yahoo.co.uk Wed Jun 16 23:07:11 2010 From: breamoreboy at yahoo.co.uk (Mark Lawrence) Date: Wed, 16 Jun 2010 22:07:11 +0100 Subject: [Tutor] How to model objects aimed to persistence? In-Reply-To: <4C193690.5070103@googlemail.com> References: <4C193690.5070103@googlemail.com> Message-ID: On 16/06/2010 21:39, Knacktus wrote: > Hi everyone, > > within a python application I can easily model object association with > simple references, e.g.: > > ################################################################# > class FavoritMovies(object): > def __init__(self, movies): > self.movies = movies > > class Movie(object): > def __init__(self, name, actor): > self.name = name > self.actor = actor > > gladiator = Movie("Gladiator", "Russel Crowe") > my_favorit_movies = FavoritMovies([gladiator]) > > kung_fu_panda = Movie("Kung Fu Panda", "Jack Black") > your_favorit_movies = FavoritMovies([gladiator, kung_fu_panda]) > ################################################################## > > So far, so good. But what is best practise to prepare this data for > general persistence? It should be usable for serialisation to xml or > storing to an RDBMS or ObjectDatabase ... > > I guess I have to incorporate some kind of id for every object and use > this as reference with some kind of look-up dictionary, but I wouldn't > like it and hope that there're some other sweet pythonic solutions? > > Cheers, > > Jan > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > Hi Jan, I guess you're looking for something like the shelve or pickle modules. http://docs.python.org/library/shelve.html http://docs.python.org/library/pickle.html HTH. Mark Lawrence. From steve at pearwood.info Thu Jun 17 00:52:26 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Thu, 17 Jun 2010 08:52:26 +1000 Subject: [Tutor] =?utf-8?q?conventions_for_establishing_and_saving_default?= =?utf-8?q?_values_for=09variables?= In-Reply-To: <4C190D9A.3010403@dcsoftware.com> References: <4C190D9A.3010403@dcsoftware.com> Message-ID: <201006170852.27699.steve@pearwood.info> On Thu, 17 Jun 2010 03:44:58 am Jeff Johnson wrote: > I will send you my python script that reads and writes to a windows > style .ini file if you want me to. How is your script different from the standard ConfigParser module? -- Steven D'Aprano From steve at pearwood.info Thu Jun 17 01:19:58 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Thu, 17 Jun 2010 09:19:58 +1000 Subject: [Tutor] conventions for establishing and saving default valuesfor variables In-Reply-To: References: <193806680405.20100616073944@columbus.rr.com> Message-ID: <201006170919.58630.steve@pearwood.info> On Thu, 17 Jun 2010 03:25:03 am Alan Gauld wrote: > "R. Alan Monroe" wrote > > >> directory, I suppose. Under windows, probably the registry. > >> There's the _winreg and configparser modules. > > > > Consider using the %USERPROFILE% environment variable rather than > > the > > registry. > > How would that work? That is just a single variable that points > to the users Settings folder. Effectively their home directory in > unix terms, so you could store the config file there. But > you couldn't store the kind of data you would store in the > registry? > > I'm confused. Environment variables are not permanent storage. They only exist in RAM unless you take steps to recreate them from permanent storage. Under Linux, for example, environment variables are recreated each time you log in after being read from a config file, such as .bashrc. My .bashrc includes: export PYTHONPATH=/home/steve/python/ export PYTHONSTARTUP=/home/steve/python/startup.py So even if you wrote the values you cared about to one or more environment variable, they would disappear as soon as the user logged out or rebooted. It gets worse... Python includes the command os.putenv to set environment variables, but they are only set for subprocesses of the Python process that sets them. So for example, I can do this: >>> os.putenv('myenvvar', 'value') >>> os.system('echo $myenvvar') value 0 but if I turn to another shell (not a subshell) it doesn't exist: [steve at sylar ~]$ echo $myenvvar [steve at sylar ~]$ See also this: http://code.activestate.com/recipes/159462-how-to-set-environment-variables/ So unless I've missed something exceedingly subtle, writing to environment variables is not a solution to the problem of saving default values. It's not even part of a solution. -- Steven D'Aprano From steve at pearwood.info Thu Jun 17 01:47:13 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Thu, 17 Jun 2010 09:47:13 +1000 Subject: [Tutor] How to model objects aimed to persistence? In-Reply-To: <4C193690.5070103@googlemail.com> References: <4C193690.5070103@googlemail.com> Message-ID: <201006170947.14116.steve@pearwood.info> On Thu, 17 Jun 2010 06:39:44 am Knacktus wrote: > So far, so good. But what is best practise to prepare this data for > general persistence? It should be usable for serialisation to xml or > storing to an RDBMS or ObjectDatabase ... Oh wow, deja vu... this is nearly the same question as just asked a day or so ago, in the thread "conventions for establishing and saving default values for?variables". The answer I give will be more or less the same as was already given in that thread: Use ConfigParser for ini-style config files. Use pickle or shelve for serialising arbitrary Python objects. You probably shouldn't use marshal, as that's awfully limited and really only designed for serialising Python byte code. You can roll your own XML solution using the various XML modules in the standard library, or use plistlib, an XML-based storage format borrowed from Mac OS X. Or one of the other standard serialisers like JSON or YAML, although YAML is not in the standard library yet. Or you can use any one of many different databases, although that's probably massive overkill. > I guess I have to incorporate some kind of id for every object and > use this as reference with some kind of look-up dictionary, "Have to"? Certainly not. If your data doesn't need an ID field, there's no need to add one just for serialisation. It would be a pretty bizarre serialiser that couldn't handle this: {key: value} but could handle this: ({id: key}, {key: value}) > but I > wouldn't like it and hope that there're some other sweet pythonic > solutions? There's a few... :) By the way, looking at your class name: class FavoritMovies(object): I can forgive the American (mis)spelling of Favo(u)rite, but why have you dropped the E off the end of "favorite"? I'd almost think your keyboard was broken, but no, you have E in Movies and object. Deliberate misspellings in class and variable names will cost you *far* more in debugging time when you forget to misspell the words than they will save you in typing. Trust me on this. -- Steven D'Aprano From alan.gauld at btinternet.com Thu Jun 17 02:17:13 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Thu, 17 Jun 2010 01:17:13 +0100 Subject: [Tutor] How to model objects aimed to persistence? References: <4C193690.5070103@googlemail.com> <201006170947.14116.steve@pearwood.info> Message-ID: "Steven D'Aprano" wrote > Deliberate misspellings in class and variable names > will cost you *far* more in debugging time when you > forget to misspell the words than they will save you > in typing. Trust me on this. I don't normally do "me too" postings but this is such a big deal that I just have to concur with Steven. It doesn't matter too much if you abbreviate local variables but anything that might be exposed at the module level and visible across imports should be spelled in full. It will only cause grief and pain later, if not to you then to anyone who imports your code... -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From jf_byrnes at comcast.net Thu Jun 17 04:35:07 2010 From: jf_byrnes at comcast.net (Jim Byrnes) Date: Wed, 16 Jun 2010 21:35:07 -0500 Subject: [Tutor] Tkinter - master attribute In-Reply-To: <428097.47271.qm@web86702.mail.ird.yahoo.com> References: <4C0E7204.6080908@comcast.net> <4C17E4FF.6020705@comcast.net> <428097.47271.qm@web86702.mail.ird.yahoo.com> Message-ID: <4C1989DB.2010009@comcast.net> ALAN GAULD wrote: > > >> I still am having trouble understanding the use of "master" in >> Tkinter. I think the problem is I can't find any reference that explains the >> concept around master, > > If you read the GUI topic in my tutorial it explains the concept > of a containment tree that is common to ost GUI frameworks > including Tkinter. All widgets belong to a parent or master > widget until you get to some kind of root or main window that > is the master odf all its sub widgets. I'll make it my next stop. > When you delete a window you delete the master and it deletes > all its children. The children delete their children, and so on until > all the widgets making up the window are deleted. Thats how GUIs work. > Similarly if you add a widget to a window you must tell the new > widget where within the containment tree it sits, you tell it who > its master is. Usually the widget will register itself with its master. > >> put the word spam on a Button I found a reference that said you type the word >> text followed by an equal sign followed by spam in quotes. > > That's slightly different in that text is an attribute of the widget itself. > By assigning 'Spam' to the attribute you control the look of that particular > Button widget. OK. That was the best example I could come up with to convey my confusion concerning master. I could look at a reference and see that in that context the word text had a special purpose, I couldn't do that with master. > class CanvasEventsDemo(canvasDraw.CanvasEventsDemo): > def __init__(self, parent=None): > canvasDraw.CanvasEventsDemo.__init__(self, parent) > > Here parent is being used instead of master. Thats quite common. Its usage like this that tends to confuse me. If I change all occurrences of of parent to Xparent the program runs. If I replace parent with master the program runs. If I replace canvas.master with canvas.xmaster I get an error. >> self.canvas.master.bind('', self.onMoveOvals) > > Here the master attribute is being accessed. That is an attribute > of the canvas widget. > >> word master appears only twice in the entire script so it is not defined >> somewhere else in the script. > > It is an inherited attribute and is inherited by all widgets > although from where is a little bit mysterious - see below... > >> AttributeError: Canvas instance has no attribute >> 'masterx' >> >> So the Canvas does not have a masterx attribute but does have >> one called master. Maybe the bottom line question is where can I look to >> see a list of a widgets attributes? > > You can use dir() or help(). > However in Tkinter it is further complicated by the mapping of Tkinter > to the underlying Tk widgets. It is not always 1-1 and some attributes > are implemented by the Tk tookit rather than at the Tkinter level and > these do not always show up in dir(). Master appears to be one of these. > > However, on digging a little deeper it seems there is a subtle distinction > in Tkinter between the containment hierarchy and the geometry manager > hierarchy. I confess that I've never noticed this before and have only > skimmed the material(Grayson's Tkinter book) but it seems that master > refers to the GM hierarchy and parent to the containment one. In most > cases they will be the same but they can be different. But because of > this master seems to be implemented somewhere in the GM code > rather than the widget code... > > In most cases you can ignore that - as I have been doing for the last 10 years! :-) > Just use master as an inherited attribute that is present in all widgets. OK, good. This is what I was looking for, an explicit statement of what master is. >> Sorry to be so dense about this but I just don't get it yet. > > You are not being dense but asking rather deep questions which > probably need someone who understands the Tkinter implementatioon > to answer. You probably don't really need to know the detail, just accept > that master will be the attribute and it will be there in each widget class > you use. I really wasn't trying to delve deep into the innards of Tkinter, it just seemed like master was appearing like magic and I just wanted to nail it down so I could get on learning Python. > If I get the time I will try to track this down further now that you have > piqued my curiosity. > > HTH, It does, I finally feel like I have a handle on it. Thanks for your time and patience. Regards, Jim > Alan G. > From payal-python at scriptkitchen.com Thu Jun 17 04:48:19 2010 From: payal-python at scriptkitchen.com (Payal) Date: Wed, 16 Jun 2010 19:48:19 -0700 Subject: [Tutor] pickling/shelve classes Message-ID: <20100617024819.GA8835@scriptkitchen.com> Hi all, Can someone please help in this below? class F(object) : ...: def __init__(self, amt) : self.amt = amt ...: def dis(self) : print 'Amount : ', self.amt ...: def add(self, na) : ...: self.amt += na ...: F.dis(self) pickle.dumps(F) gives PicklingError: Can't pickle : it's not found as __main__.F What is my mistake? I want to pickle and shelve classes as well as instances. With warm regards, -Payal -- From knacktus at googlemail.com Thu Jun 17 06:07:26 2010 From: knacktus at googlemail.com (Knacktus) Date: Thu, 17 Jun 2010 06:07:26 +0200 Subject: [Tutor] How to model objects aimed to persistence? In-Reply-To: References: <4C193690.5070103@googlemail.com> <201006170947.14116.steve@pearwood.info> Message-ID: <4C199F7E.1080201@googlemail.com> Am 17.06.2010 02:17, schrieb Alan Gauld: > "Steven D'Aprano" wrote >> Deliberate misspellings in class and variable names will cost you >> *far* more in debugging time when you forget to misspell the words >> than they will save you in typing. Trust me on this. Thanks for that hint. I can imagine the nightmares ... It was just a spelling mistake. English is not my native language and I sometime tend to skip trailing "e"s ;-). But I think I need to clarify my question a bit. The point I'm unsure with is how to best model references in python for persistence when not using pickle or any dedicated python. Python doesn't even need names as reference to the objects location in memory. I could do something like this: ########################################################################### my_favourite_movies = FavouriteMovies([Movie("Gladiator", "Russel Crowe")]) ########################################################################### When I want to rebuild the data from a xml file or database, my objects somehow need to know which references to other objects they hold. I don't now wether I have to use explicit indices in my python code to make it "xml-ready" and if that's the case, how to do it smoothly. Or whether there's some other trick. Cheers, Jan From nbr1ninrsan7 at yahoo.com Thu Jun 17 09:10:32 2010 From: nbr1ninrsan7 at yahoo.com (Independent Learner) Date: Thu, 17 Jun 2010 00:10:32 -0700 (PDT) Subject: [Tutor] Importing files not located on the home directory or standardard library Message-ID: <962622.95064.qm@web120013.mail.ne1.yahoo.com> I am having trouble figuring out how to import modules not located on the home directory or standard library of modules. Meaning say I write a module and instead of saving it on the home directory I save in a folder in my desktop. I do not know how to retrieve it by way of the import statement. I know it has something to do with the PYTHONPATH or .pth,? however I am not sure how to configure these, right now I am reading Learning Pythong 3rd ed. by Mark Lutz and unfortnately that book has a lot more words then examples so I am usually left to figure alot of the concepts myself while rereading word for word to try to figure out how the heck it applies to IDLE and practical uses for code. I thoroughly understand modules and how to import them when they are in the home directory or standard library, thats pretty simple, however like I said I do not know how to import files outside of these directories. I am using windows 7 and python 2.6.5 Lets say I want to load a file called quiz located in C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.4 How would I configure PYTHONPATH or .pth? or what ever to import this file from IDLE I am also having slight trouble understanding module packages as well, though I suspect it has something to do with not knowing how to configure PYTHONPATH or .pth files Thanks =) ~Julius H. -------------- next part -------------- An HTML attachment was scrubbed... URL: From k247d0 at gmail.com Thu Jun 17 09:28:37 2010 From: k247d0 at gmail.com (KB SU) Date: Thu, 17 Jun 2010 00:28:37 -0700 Subject: [Tutor] help Message-ID: help -------------- next part -------------- An HTML attachment was scrubbed... URL: From eike.welk at gmx.net Thu Jun 17 11:11:11 2010 From: eike.welk at gmx.net (Eike Welk) Date: Thu, 17 Jun 2010 11:11:11 +0200 Subject: [Tutor] pickling/shelve classes In-Reply-To: <20100617024819.GA8835@scriptkitchen.com> References: <20100617024819.GA8835@scriptkitchen.com> Message-ID: <201006171111.11757.eike.welk@gmx.net> Hello Payal! On Thursday June 17 2010 04:48:19 Payal wrote: > Hi all, > Can someone please help in this below? > > class F(object) : > ...: def __init__(self, amt) : self.amt = amt > ...: def dis(self) : print 'Amount : ', self.amt > ...: def add(self, na) : > ...: self.amt += na > ...: F.dis(self) > > pickle.dumps(F) > gives PicklingError: Can't pickle : it's not found > as __main__.F I think it is a bug in IPython: I can do this in regular Python, but in IPython I get the same error that you get: Python 2.6.2 (r262:71600, Mar 29 2010, 15:30:01) [GCC 4.4.1 [gcc-4_4-branch revision 150839]] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> class A(object):pass ... >>> import pickle >>> pickle.dumps(A) 'c__main__\nA\np0\n.' >>> You should file a bug report in their bug tracker: http://github.com/ipython/ipython/issues Eike. From modulok at gmail.com Thu Jun 17 11:23:57 2010 From: modulok at gmail.com (Modulok) Date: Thu, 17 Jun 2010 03:23:57 -0600 Subject: [Tutor] help In-Reply-To: References: Message-ID: Solution: width times height. On 6/17/10, KB SU wrote: > help > From modulok at gmail.com Thu Jun 17 11:25:57 2010 From: modulok at gmail.com (Modulok) Date: Thu, 17 Jun 2010 03:25:57 -0600 Subject: [Tutor] Trouble with sockets... Message-ID: List, I'm new to sockets and having trouble. I tried to write a simple client/server program (see code below). The client would send a string to the server. The server would echo that back to the client. PROBLEM: I can send data to the server, and get data back, but only for the first call to the 'sendall()' method. If I try to call it in a loop on the client, to print a count-down, only the first call gets echoed. Clearly, I'm missing something. EXAMPLE: (They're on the same physical machine.) Shell on the server: Modulok at modUnix> ./socket_server.py Listening for clients... Got connection from 192.168.1.1 Shell on the client: Modulok at modUnix> ./latency_client.py 192.168.1.1 2554 0 What I wanted: [-]Modulok at modUnix> ./latency_client.py 192.168.1.1 2554 0 1 2 CODE: ################################ # The client program: ################################ import socket import sys def main(): '''Send data to a server and receive the data echoed back to us.''' s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.connect( ('192.168.1.1', 2554) ) for i in range(3): s.sendall(str(i)) print s.recv(1024) s.close() # Execution starts here: try: main() except KeyboardInterrupt: sys.exit("Aborting.") ################################ # The server program: ################################ import socket import sys def main(): '''Listen for a client and echo data back to them.''' s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind( ('192.168.1.1', 2554) ) s.listen(5) print "Listening for clients..." while True: channel, client = s.accept() print "Got connection from %s" % client[0] message = channel.recv(1024) channel.send(message) channel.close() # Execution starts here: try: main() except KeyboardInterrupt: sys.exit("Aborting.") From hugo.yoshi at gmail.com Thu Jun 17 13:13:55 2010 From: hugo.yoshi at gmail.com (Hugo Arts) Date: Thu, 17 Jun 2010 13:13:55 +0200 Subject: [Tutor] conventions for establishing and saving default valuesfor variables In-Reply-To: <201006170919.58630.steve@pearwood.info> References: <193806680405.20100616073944@columbus.rr.com> <201006170919.58630.steve@pearwood.info> Message-ID: On Thu, Jun 17, 2010 at 1:19 AM, Steven D'Aprano wrote: > On Thu, 17 Jun 2010 03:25:03 am Alan Gauld wrote: >> "R. Alan Monroe" wrote >> >> >> directory, I suppose. Under windows, probably the registry. >> >> There's the _winreg and configparser modules. >> > >> > Consider using the %USERPROFILE% environment variable rather than >> > the >> > registry. >> >> How would that work? That is just a single variable that points >> to the users Settings folder. Effectively their home directory in >> unix terms, so you could store the config file there. But >> you couldn't store the kind of data you would store in the >> registry? >> >> I'm confused. > > [snip explanation of environment variables] > > So unless I've missed something exceedingly subtle, writing to > environment variables is not a solution to the problem of saving > default values. It's not even part of a solution. > Just speculation here, but.. I suppose what he's suggesting is that you use ConfigParser on both linux and windows, rather than the registry on one platform and a config file on the other. on windows you'd then place the config file in the %USERPROFILE% directory. It's actually a rather good idea, not having to bother with the registry saves you a lot of work. Hugo From steve at pearwood.info Thu Jun 17 14:20:24 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Thu, 17 Jun 2010 22:20:24 +1000 Subject: [Tutor] help In-Reply-To: References: Message-ID: <201006172220.25156.steve@pearwood.info> On Thu, 17 Jun 2010 05:28:37 pm KB SU wrote: > help No no, don't tell us what you need help about! I love guessing games! Let me see now... I'm guessing that your problem is that don't know how to work out the length of a string. Here's one way: string = "something" count = 1 for char in string: count *= 10 import math print "The string has", math.log10(count), "characters." There's probably a shorter way too. -- Steven D'Aprano From breamoreboy at yahoo.co.uk Thu Jun 17 14:30:08 2010 From: breamoreboy at yahoo.co.uk (Mark Lawrence) Date: Thu, 17 Jun 2010 13:30:08 +0100 Subject: [Tutor] help In-Reply-To: References: Message-ID: On 17/06/2010 08:28, KB SU wrote: > help > > > > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor Help, I need somebody, Help, not just anybody, Help, you know I need someone, help. I'll leave you to find out the rests of the lyrics. :) Mark Lawrence. From alan.gauld at btinternet.com Thu Jun 17 19:14:16 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Thu, 17 Jun 2010 18:14:16 +0100 Subject: [Tutor] How to model objects aimed to persistence? References: <4C193690.5070103@googlemail.com> <201006170947.14116.steve@pearwood.info> <4C199F7E.1080201@googlemail.com> Message-ID: "Knacktus" wrote ########################################################################### > my_favourite_movies = FavouriteMovies([Movie("Gladiator", "Russel > Crowe")]) > ########################################################################### > > When I want to rebuild the data from a xml file or database, my > objects somehow need to know which references to other objects they > hold. OK, If you limit yourself to XML or a database then yes you will need an ID and use the IDs as references. Thats why Pickle/Shelve are so convenient for persistence - they don;t need the references, you can just pickle the list of objects, or whatever. HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From alan.gauld at btinternet.com Thu Jun 17 19:21:59 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Thu, 17 Jun 2010 18:21:59 +0100 Subject: [Tutor] Importing files not located on the home directory orstandardard library References: <962622.95064.qm@web120013.mail.ne1.yahoo.com> Message-ID: "Independent Learner" wrote > Lets say I want to load a file called quiz located in > C:\Users\Julius > Hernandez\Desktop\Python2.6.5\Online Course\Chp.4 > > How would I configure PYTHONPATH or .pth or what ever > to import this file from IDLE The IDLE bit is irrelevant its how the underlying Python interpreter does things that matters. You would need to set your PYTHONPATH environment variable to include the directory containing your modules. Do you know how to add values to a Windows Environment variable? If not go to the Getting Started topic of my tutor for an example of setting the PATH variable (You do the same but for PYTHONPATH, the only difference is you might need to create it if it doesn't already exist!) Otherwise, Where are you having problems? -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From lowelltackett at yahoo.com Thu Jun 17 20:22:20 2010 From: lowelltackett at yahoo.com (Lowell Tackett) Date: Thu, 17 Jun 2010 11:22:20 -0700 (PDT) Subject: [Tutor] help In-Reply-To: Message-ID: <785881.53712.qm@web110113.mail.gq1.yahoo.com> >From the virtual desk of Lowell Tackett? --- On Thu, 6/17/10, Mark Lawrence wrote: From: Mark Lawrence Subject: Re: [Tutor] help To: tutor at python.org Date: Thursday, June 17, 2010, 8:30 AM On 17/06/2010 08:28, KB SU wrote: > help > > > > > _______________________________________________ > Tutor maillist? -? Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor Help, I need somebody, Help, not just anybody, Help, you know I need someone, help. I'll leave you to find out the rests of the lyrics. :) Mark Lawrence. You're "dating" yourself!? (I was in 'Nam when that song came out.) _______________________________________________ Tutor maillist? -? Tutor at python.org To unsubscribe or change subscription options: http://mail.python.org/mailman/listinfo/tutor -------------- next part -------------- An HTML attachment was scrubbed... URL: From eike.welk at gmx.net Thu Jun 17 20:49:00 2010 From: eike.welk at gmx.net (Eike Welk) Date: Thu, 17 Jun 2010 20:49:00 +0200 Subject: [Tutor] pickling/shelve classes In-Reply-To: <201006171111.11757.eike.welk@gmx.net> References: <20100617024819.GA8835@scriptkitchen.com> <201006171111.11757.eike.welk@gmx.net> Message-ID: <201006172049.00367.eike.welk@gmx.net> On Thursday June 17 2010 11:11:11 Eike Welk wrote: > You should file a bug report in their bug tracker: > http://github.com/ipython/ipython/issues I believe tthis is the bug: http://github.com/ipython/ipython/issues/#issue/29 It seems that objects defined on IPython's top-level can't be pickled. Eike. From breamoreboy at yahoo.co.uk Thu Jun 17 20:53:31 2010 From: breamoreboy at yahoo.co.uk (Mark Lawrence) Date: Thu, 17 Jun 2010 19:53:31 +0100 Subject: [Tutor] help In-Reply-To: <785881.53712.qm@web110113.mail.gq1.yahoo.com> References: <785881.53712.qm@web110113.mail.gq1.yahoo.com> Message-ID: On 17/06/2010 19:22, Lowell Tackett wrote: > >> From the virtual desk of Lowell Tackett > > --- On Thu, 6/17/10, Mark Lawrence wrote: > > From: Mark Lawrence > Subject: Re: [Tutor] help > To: tutor at python.org > Date: Thursday, June 17, 2010, 8:30 AM > > On 17/06/2010 08:28, KB SU wrote: >> help >> > > Help, I need somebody, > Help, not just anybody, > Help, you know I need someone, help. > > I'll leave you to find out the rests of the lyrics. :) > > Mark Lawrence. > > You're "dating" yourself! (I was in 'Nam when that song came out.) Jeesh, unlucky you :( (I was in shorts at our village primary school) Another lyric, "I hope I die before I get old", similar sort of era, eh? :) Regards. Mark Lawrence. > > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor From kaushalshriyan at gmail.com Thu Jun 17 20:53:49 2010 From: kaushalshriyan at gmail.com (Kaushal Shriyan) Date: Fri, 18 Jun 2010 00:23:49 +0530 Subject: [Tutor] collectd application Message-ID: Hi, For example I do wget -O file.png "http://collectd.example.com/collectd/cgi-bin/collection.cgi?action=show_plugin;host=testdb;timespan=day;plugin=mysql" for a single host "testdb" and plugin "mysql" I do /usr/bin/mime-construct --header 'Sender: MOR_FAX at TEST.COM' --header 'From: MOR_FAX at TEST.COM' --to your at mail.com --subject 'Email test' --file-attach /var/tmp/file.png That would be a manual way of doing it. I do have numerous servers and multiple plugins. Basically i would like to do it without manual intervention. Please suggest further to send multiple png files from multiple servers with multiple collectd plugins. is that possible using python ? Thanks, Kaushal From rick at niof.net Thu Jun 17 22:41:08 2010 From: rick at niof.net (Rick Pasotto) Date: Thu, 17 Jun 2010 16:41:08 -0400 Subject: [Tutor] string encoding Message-ID: <20100617204108.GA4846@niof.net> I'm using BeautifulSoup to process a webpage. One of the fields has a unicode character in it. (It's the 'registered trademark' symbol.) When I try to write this string to another file I get this error: UnicodeEncodeError: 'ascii' codec can't encode characters in position 31-32: ordinal not in range(128) In the interpreter the offending string portion shows as: 'Realtors\xc2\xae'. How can I deal with this single string? The rest of the document works fine. -- "Freedom can't be kept for nothing. If you set a high value on liberty, you must set a low value on everything else." -- Lucius Annaeus Seneca, 65 A.D. Rick Pasotto rick at niof.net http://www.niof.net From lie.1296 at gmail.com Fri Jun 18 04:24:25 2010 From: lie.1296 at gmail.com (Lie Ryan) Date: Fri, 18 Jun 2010 12:24:25 +1000 Subject: [Tutor] string encoding In-Reply-To: <20100617204108.GA4846@niof.net> References: <20100617204108.GA4846@niof.net> Message-ID: On 06/18/10 06:41, Rick Pasotto wrote: > I'm using BeautifulSoup to process a webpage. One of the fields has a > unicode character in it. (It's the 'registered trademark' symbol.) When > I try to write this string to another file I get this error: > > UnicodeEncodeError: 'ascii' codec can't encode characters in position 31-32: ordinal not in range(128) > > In the interpreter the offending string portion shows as: 'Realtors\xc2\xae'. > > How can I deal with this single string? The rest of the document works > fine. You need to tell BeautifulSoup the encoding of the HTML document. You can encode this information in either the: - (preferred) Encoding is specified externally from HTTP Header ContentType declaration, e.g.: Content-Type: text/html; charset=utf-8 - HTML ContentType declaration: e.g. - XML declaration -- for XHTML document used for parsing using XML parser (hint: BeautifulSoup isn't XML/XHTML parser), e.g.: However, BeautifulSoup will also uses some heuristics to *guess* the encoding of a tag soup that doesn't have a proper encoding. So, the most likely reason is this, from Beautiful Soup's FAQ: http://www.crummy.com/software/BeautifulSoup/documentation.html#Why can't Beautiful Soup print out the non-ASCII characters I gave it? """ Why can't Beautiful Soup print out the non-ASCII characters I gave it? If you're getting errors that say: "'ascii' codec can't encode character 'x' in position y: ordinal not in range(128)", the problem is probably with your Python installation rather than with Beautiful Soup. Try printing out the non-ASCII characters without running them through Beautiful Soup and you should have the same problem. For instance, try running code like this: latin1word = 'Sacr\xe9 bleu!' unicodeword = unicode(latin1word, 'latin-1') print unicodeword If this works but Beautiful Soup doesn't, there's probably a bug in Beautiful Soup. However, if this doesn't work, the problem's with your Python setup. Python is playing it safe and not sending non-ASCII characters to your terminal. There are two ways to override this behavior. 1. The easy way is to remap standard output to a converter that's not afraid to send ISO-Latin-1 or UTF-8 characters to the terminal. import codecs import sys streamWriter = codecs.lookup('utf-8')[-1] sys.stdout = streamWriter(sys.stdout) codecs.lookup returns a number of bound methods and other objects related to a codec. The last one is a StreamWriter object capable of wrapping an output stream. 2. The hard way is to create a sitecustomize.py file in your Python installation which sets the default encoding to ISO-Latin-1 or to UTF-8. Then all your Python programs will use that encoding for standard output, without you having to do something for each program. In my installation, I have a /usr/lib/python/sitecustomize.py which looks like this: import sys sys.setdefaultencoding("utf-8") For more information about Python's Unicode support, look at Unicode for Programmers or End to End Unicode Web Applications in Python. Recipes 1.20 and 1.21 in the Python cookbook are also very helpful. Remember, even if your terminal display is restricted to ASCII, you can still use Beautiful Soup to parse, process, and write documents in UTF-8 and other encodings. You just can't print certain strings with print. """ From rick at niof.net Fri Jun 18 06:21:25 2010 From: rick at niof.net (Rick Pasotto) Date: Fri, 18 Jun 2010 00:21:25 -0400 Subject: [Tutor] string encoding In-Reply-To: References: <20100617204108.GA4846@niof.net> Message-ID: <20100618042125.GM4846@niof.net> On Fri, Jun 18, 2010 at 12:24:25PM +1000, Lie Ryan wrote: > On 06/18/10 06:41, Rick Pasotto wrote: > > I'm using BeautifulSoup to process a webpage. One of the fields has a > > unicode character in it. (It's the 'registered trademark' symbol.) When > > I try to write this string to another file I get this error: > > > > UnicodeEncodeError: 'ascii' codec can't encode characters in position 31-32: ordinal not in range(128) > > > > In the interpreter the offending string portion shows as: 'Realtors\xc2\xae'. > > > > How can I deal with this single string? The rest of the document works > > fine. > > You need to tell BeautifulSoup the encoding of the HTML document. You > can encode this information in either the: > > - (preferred) Encoding is specified externally from HTTP Header > ContentType declaration, e.g.: > Content-Type: text/html; charset=utf-8 > > - HTML ContentType declaration: e.g. > The document has: When I look at the document in vim and when I 'print' in python I see the two characters of an acented capital A and the circled 'r'. > latin1word = 'Sacr\xe9 bleu!' > unicodeword = unicode(latin1word, 'latin-1') > print unicodeword TypeError: decoding Unicode is not supported > If this works but Beautiful Soup doesn't, there's probably a bug in > Beautiful Soup. However, if this doesn't work, the problem's with your > Python setup. Python is playing it safe and not sending non-ASCII > characters to your terminal. There are two ways to override this behavior. > > 1. The easy way is to remap standard output to a converter that's not > afraid to send ISO-Latin-1 or UTF-8 characters to the terminal. > > import codecs > import sys > streamWriter = codecs.lookup('utf-8')[-1] > sys.stdout = streamWriter(sys.stdout) > > codecs.lookup returns a number of bound methods and other objects > related to a codec. The last one is a StreamWriter object capable of > wrapping an output stream. Those four lines executed but I still get TypeError: decoding Unicode is not supported > Remember, even if your terminal display is restricted to ASCII, you can > still use Beautiful Soup to parse, process, and write documents in UTF-8 > and other encodings. You just can't print certain strings with print. I can print the string fine. It's f.write(string_with_unicode) that fails with: UnicodeEncodeError: 'ascii' codec can't encode characters in position 31-32: ordinal not in range(128) Shouldn't I be able to f.write() *any* 8bit byte(s)? repr() gives: u"Realtors\\xc2\\xae" BTW, I'm running python 2.5.5 on debian linux. -- "Making fun of born-again christians is like hunting dairy cows with a high powered rifle and scope." -- P.J. O'Rourke Rick Pasotto rick at niof.net http://www.niof.net From steve at pearwood.info Fri Jun 18 07:45:17 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Fri, 18 Jun 2010 15:45:17 +1000 Subject: [Tutor] collectd application In-Reply-To: References: Message-ID: <201006181545.17738.steve@pearwood.info> On Fri, 18 Jun 2010 04:53:49 am Kaushal Shriyan wrote: [...] > is that possible using python ? Yes. Python is a Turing complete language, it can do anything that any other language can do. This site will probably help you: http://www.catb.org/%7Eesr/faqs/smart-questions.html Good luck, and we look forward to you coming back with a better question! -- Steven D'Aprano From lang at tharin.com Fri Jun 18 07:54:05 2010 From: lang at tharin.com (Lang Hurst) Date: Thu, 17 Jun 2010 22:54:05 -0700 Subject: [Tutor] sqlite3 select extra characters Message-ID: <4C1B09FD.3060803@tharin.com> Is there a way to just return the values when using sqlite3? If I: names = c.execute('select names from students') for name in names: print names I get the list I want, but they look like (u'Cleese, John') (u'Jones, Terry') (u'Gillaim, Terry') is there a way to just return Cleese, John Jones, Terry Gillaim, Terry ? It seems a shame to have to run the answers through a stip process. -- There are no stupid questions, just stupid people. From alan.gauld at btinternet.com Fri Jun 18 09:20:41 2010 From: alan.gauld at btinternet.com (Alan Gauld) Date: Fri, 18 Jun 2010 08:20:41 +0100 Subject: [Tutor] sqlite3 select extra characters References: <4C1B09FD.3060803@tharin.com> Message-ID: "Lang Hurst" wrote > Is there a way to just return the values when using sqlite3? I don't think so, select returns a tuple of values, even if there is only one value. > I get the list I want, but they look like > > (u'Cleese, John') > is there a way to just return > > Cleese, John > > It seems a shame to have to run the answers through a stip process. It's hardly a major effort to index the item? print name[0] instead of print name HTH, -- Alan Gauld Author of the Learn to Program web site http://www.alan-g.me.uk/ From steve at pearwood.info Fri Jun 18 11:22:52 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Fri, 18 Jun 2010 19:22:52 +1000 Subject: [Tutor] sqlite3 select extra characters In-Reply-To: <4C1B09FD.3060803@tharin.com> References: <4C1B09FD.3060803@tharin.com> Message-ID: <201006181922.52798.steve@pearwood.info> On Fri, 18 Jun 2010 03:54:05 pm Lang Hurst wrote: > Is there a way to just return the values when using sqlite3? > > If I: > > names = c.execute('select names from students') > for name in names: print names What is c? A Cursor or a Connection object? It probably doesn't make any real difference, but it could, and so you should say. > I get the list I want, but they look like > > (u'Cleese, John') > (u'Jones, Terry') > (u'Gillaim, Terry') I doubt it. Did you mean this? (u'Cleese, John',) Note the comma at the end. A subtle difference, but a HUGE one. Punctuation is important: it's what makes the difference between: "Let's eat, Grandma!" and "Let's eat Grandma!" In Python, the comma makes it a tuple, rather than a meaningless pair of parentheses. > is there a way to just return > > Cleese, John > Jones, Terry > Gillaim, Terry No, because you're not *returning* anything, you're *printing*, and printing a tuple prints the opening and closing brackets plus the repr() of each internal object. Compare the following: >>> t = (u"Cleese, John",) # a tuple like that returned by execute >>> print t # print the tuple (u'Cleese, John',) >>> print t[0] # print the unicode string alone Cleese, John >>> print repr(t[0]) # print the unicode string's repr() u'Cleese, John' This is fundamental stuff: objects are not their printable representation, any more than you are a photo of you. What is printed is not the same as the object itself. Every object has its own printable representation. In some cases it looks exactly the same as the way you enter the object as a literal: >>> print 42 42 in other cases it is not: >>> print "Hello world" Hello world >>> print repr("Hello world") 'Hello world' >>> print "Hello world" # includes a tab character Hello world >>> print repr("Hello world") 'Hello\tworld' In this case, the object returned by execute is a list of tuples. If there is only a single object in each tuple, it is still a tuple, and it still prints as a tuple. If you want to print something other than a tuple, don't print the tuple: names = c.execute('select names from students') for t in names: name = t[0] # Extract the first item from each tuple. print name Of course you can combine the two lines inside the loop: print t[0] > It seems a shame to have to run the answers through a stip process. It would be more of a shame if execute sometimes returned a list of tuples, and sometimes a list of other objects, with no easy way before hand of knowing what it would return. -- Steven D'Aprano From payal-python at scriptkitchen.com Fri Jun 18 12:02:13 2010 From: payal-python at scriptkitchen.com (Payal) Date: Fri, 18 Jun 2010 03:02:13 -0700 Subject: [Tutor] pickling/shelve classes In-Reply-To: <201006171111.11757.eike.welk@gmx.net> References: <20100617024819.GA8835@scriptkitchen.com> <201006171111.11757.eike.welk@gmx.net> Message-ID: <20100618100213.GA27438@scriptkitchen.com> On Thu, Jun 17, 2010 at 11:11:11AM +0200, Eike Welk wrote: > I think it is a bug in IPython: I can do this in regular Python, but in > IPython I get the same error that you get: > Thanks a lot. It works in normal python. Thanks again. With warm regards, -Payal -- From payal-python at scriptkitchen.com Fri Jun 18 12:22:26 2010 From: payal-python at scriptkitchen.com (Payal) Date: Fri, 18 Jun 2010 03:22:26 -0700 Subject: [Tutor] how to shelve classes Message-ID: <20100618102226.GA27650@scriptkitchen.com> Hi, I want to carry my classes around, so I wrote foo.py as, #!/usr/bin/python import pickle, shelve f = shelve.open('movies') class F(object) : def __init__(self, amt) : self.amt = amt def dis(self) : print 'Amount : ', self.amt def add(self, na) : self.amt += na F.dis(self) f['k'] = F x=F(99) f['k2']=x Now in python interpreter I get, >>> import shelve >>> f = shelve.open('movies') >>> F2=f['k'] Traceback (most recent call last): File "", line 1, in File "/usr/lib/python2.6/shelve.py", line 122, in __getitem__ value = Unpickler(f).load() AttributeError: 'module' object has no attribute 'F' How do I carry around my classes and instances? With warm regards, -Payal -- From lie.1296 at gmail.com Fri Jun 18 12:35:44 2010 From: lie.1296 at gmail.com (Lie Ryan) Date: Fri, 18 Jun 2010 20:35:44 +1000 Subject: [Tutor] string encoding In-Reply-To: <20100618042125.GM4846@niof.net> References: <20100617204108.GA4846@niof.net> <20100618042125.GM4846@niof.net> Message-ID: On 06/18/10 14:21, Rick Pasotto wrote: >> Remember, even if your terminal display is restricted to ASCII, you can >> still use Beautiful Soup to parse, process, and write documents in UTF-8 >> and other encodings. You just can't print certain strings with print. > > I can print the string fine. It's f.write(string_with_unicode) that fails with: > > UnicodeEncodeError: 'ascii' codec can't encode characters in position 31-32: ordinal not in range(128) > > Shouldn't I be able to f.write() *any* 8bit byte(s)? > > repr() gives: u"Realtors\\xc2\\xae" > > BTW, I'm running python 2.5.5 on debian linux. > The FAQ explains half of it, except that in your case, substitute what it says about "terminal" with "file object". Python plays it safe and does not implicitly encode a unicode string when writing into a file. If you have a unicode string and you want to .write() that unicode string to a file, you need to .encode() the string first, so: string_with_unicode = u"Realtors\xc2\xae" f.write(string_with_unicode.encode('utf-8')) otherwise, you can use the codecs module to wrap the file object: f = codecs.open('filename.txt', 'w', encoding="utf-8") f.write(string_with_unicode) # now you can send unicode string to f From davea at ieee.org Fri Jun 18 13:50:28 2010 From: davea at ieee.org (Dave Angel) Date: Fri, 18 Jun 2010 07:50:28 -0400 Subject: [Tutor] string encoding In-Reply-To: <20100618042125.GM4846@niof.net> References: <20100617204108.GA4846@niof.net> <20100618042125.GM4846@niof.net> Message-ID: <4C1B5D84.6090302@ieee.org> Rick Pasotto wrote: > > I can print the string fine. It's f.write(string_with_unicode) that fails with: > > UnicodeEncodeError: 'ascii' codec can't encode characters in position 31-32: ordinal not in range(128) > > Shouldn't I be able to f.write() *any* 8bit byte(s)? > > repr() gives: u"Realtors\\xc2\\xae" > > BTW, I'm running python 2.5.5 on debian linux. > > You can write any 8 bit string. But you have a Unicode string, which is 16 or 32 bits per character. To write it to a file, it must be encoded, and the default encoder is ASCII. The cure is to encode it yourself, using the encoding that your spec calls for. I'll assume utf8 below: >>> name = u"Realtors\xc2\xae" >>> repr(name) "u'Realtors\\xc2\\xae'" >>> outfile = open("junk.txt", "w") >>> outfile.write(name) Traceback (most recent call last): File "", line 1, in UnicodeEncodeError: 'ascii' codec can't encode characters in position 8-9: ordin al not in range(128) >>> outfile.write(name.encode("utf8")) >>> outfile.close() DaveA From eike.welk at gmx.net Fri Jun 18 15:16:36 2010 From: eike.welk at gmx.net (Eike Welk) Date: Fri, 18 Jun 2010 15:16:36 +0200 Subject: [Tutor] how to shelve classes In-Reply-To: <20100618102226.GA27650@scriptkitchen.com> References: <20100618102226.GA27650@scriptkitchen.com> Message-ID: <201006181516.36192.eike.welk@gmx.net> On Friday June 18 2010 12:22:26 Payal wrote: > Hi, > I want to carry my classes around, so I wrote foo.py as, > > #!/usr/bin/python > > import pickle, shelve > > f = shelve.open('movies') > > class F(object) : > def __init__(self, amt) : self.amt = amt > def dis(self) : print 'Amount : ', self.amt > def add(self, na) : > self.amt += na > F.dis(self) > > f['k'] = F > x=F(99) > f['k2']=x > > Now in python interpreter I get, > > >>> import shelve > >>> f = shelve.open('movies') > >>> F2=f['k'] > > Traceback (most recent call last): > File "", line 1, in > File "/usr/lib/python2.6/shelve.py", line 122, in __getitem__ > value = Unpickler(f).load() > AttributeError: 'module' object has no attribute 'F' > > How do I carry around my classes and instances? Classes don't really get pickled. Only a little bit of information describing the class. The class definition has to be visible to the interpreter when a class or one of its instances is unpickled. Therefore you have to import the class first (IMHO, I didn't test anything): from foo import F import shelve f = shelve.open('movies') F2=f['k'] See: http://docs.python.org/library/pickle.html#what-can-be-pickled-and-unpickled "..., classes are pickled by named reference, so the same restrictions in the unpickling environment apply. Note that none of the class?s code or data is pickled, ..." Eike. From steve at pearwood.info Fri Jun 18 16:48:59 2010 From: steve at pearwood.info (Steven D'Aprano) Date: Sat, 19 Jun 2010 00:48:59 +1000 Subject: [Tutor] Importing files not located on the home directory or standardard library In-Reply-To: <962622.95064.qm@web120013.mail.ne1.yahoo.com> References: <962622.95064.qm@web120013.mail.ne1.yahoo.com> Message-ID: <201006190049.00221.steve@pearwood.info> On Thu, 17 Jun 2010 05:10:32 pm Independent Learner wrote: > Lets say I want to load a file called quiz located in C:\Users\Julius > Hernandez\Desktop\Python2.6.5\Online Course\Chp.4 > > How would I configure PYTHONPATH or .pth? or what ever to import this > file from IDLE I don't use Windows, so I can't tell you the specific Windows commands to use, but I'll tell you the general steps and you can convert them to Windows-specific instructions. You need to: (1) Create an environment variable called PYTHONPATH; (2) Set it to the path (or paths) you want; (3) Ensure it gets automatically re-created each time you log in. (4) When you restart Python, it will add the value of PYTHONPATH to your module search path. Here is an example from Linux. I have this command in my .bashrc file: export PYTHONPATH=/home/steve/python/ The "export" shell command creates the environment variable PYTHONPATH and sets it to "/home/steve/python/". By placing it in .bashrc, it will automatically be executed each time I log in or start a new shell. Alternatively, you can use a .pth file. That's probably better if you have lots of directories to add. I've never done this, so take this with a grain of salt: (1) Find the location of your Python 2.6 installation. This is probably something like C:\Applications\Python2.6.5\ or similar. (2) Inside that directory should be another directory called "site-packages". It may or may not already have files or folders in it. (3) Find, or create, a file called ".pth" inside site-packages. You may need to instruct Windows to show hidden files. (4) Add the line: C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.4\ to that file, optionally together with C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.1\ C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.2\ C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.3\ etc. (5) Save and close the file, then restart Python. > I am also having slight trouble understanding module packages as > well, though I suspect it has something to do with not knowing how to > configure PYTHONPATH or .pth files A *module* is a single file containing Python code. Source code is name.py (also name.pyw on Windows only) while compiled byte code is name.pyc or name.pyo. There may be a few other extensions allowed on some other platforms. A *package* is a directory containing multiple modules which make up a unified whole. Not every directory containing modules is a package -- you need a special file called __init__.py for Python to treat it as a package. (That's underscore underscore i n i t underscore underscore dot p y.) If you have a directory structure like this: alpha/ +-- __init__.py +-- beta.py +-- gamma.py +-- delta/ +-- __init__.py +-- epsilon.py then you have a package alpha containing two modules beta and gamma and one sub-package delta. Now put the whole thing (the alpha directory plus it's contents) somewhere in the Python path, and it will be visible to Python. Then you can do this: import alpha and then this: x = alpha.delta.epsilon.some_function(1) y = alpha.gamma.something(2) z = alpha.something_else(3) and so forth. By the way, __init__.py doesn't have to contain anything, although it can contain code. It just needs to exist. -- Steven D'Aprano From lang at tharin.com Fri Jun 18 17:14:00 2010 From: lang at tharin.com (Lang Hurst) Date: Fri, 18 Jun 2010 08:14:00 -0700 Subject: [Tutor] sqlite3 select extra characters In-Reply-To: References: <4C1B09FD.3060803@tharin.com> Message-ID: <4C1B8D38.20802@tharin.com> Thanks. Alan Gauld wrote: > "Lang Hurst" wrote > >> Is there a way to just return the values when using sqlite3? > > I don't think so, select returns a tuple of values, even if there is > only one value. > >> I get the list I want, but they look like >> >> (u'Cleese, John') > >> is there a way to just return >> >> Cleese, John >> >> It seems a shame to have to run the answers through a stip process. > > It's hardly a major effort to index the item? > > print name[0] > > instead of > > print name > > HTH, > -- There are no stupid questions, just stupid people. From payal-tutor at scriptkitchen.com Fri Jun 18 16:11:59 2010 From: payal-tutor at scriptkitchen.com (Payal) Date: Fri, 18 Jun 2010 07:11:59 -0700 Subject: [Tutor] how to shelve classes In-Reply-To: <201006181516.36192.eike.welk@gmx.net> References: <20100618102226.GA27650@scriptkitchen.com> <201006181516.36192.eike.welk@gmx.net> Message-ID: <20100618141159.GA29599@scriptkitchen.com> On Fri, Jun 18, 2010 at 03:16:36PM +0200, Eike Welk wrote: > See: > http://docs.python.org/library/pickle.html#what-can-be-pickled-and-unpickled Thanks for the link and the explanation. With warm regards, -Payal -- From bgailer at gmail.com Fri Jun 18 19:50:45 2010 From: bgailer at gmail.com (bob gailer) Date: Fri, 18 Jun 2010 13:50:45 -0400 Subject: [Tutor] Trouble with sockets... In-Reply-To: References: Message-ID: <4C1BB1F5.5060005@gmail.com> On 6/17/2010 5:25 AM, Modulok wrote: > List, > > I'm new to sockets and having trouble. I tried to write a simple > client/server program (see code below). The client would send a string > to the server. The server would echo that back to the client. > > PROBLEM: > I can send data to the server, and get data back, but only for the > first call to the 'sendall()' method. If I try to call it in a loop on > the client, to print a count-down, only the first call gets echoed. > Clearly, I'm missing something. > > EXAMPLE: (They're on the same physical machine.) > Shell on the server: > Modulok at modUnix> ./socket_server.py > Listening for clients... > Got connection from 192.168.1.1 > > Shell on the client: > Modulok at modUnix> ./latency_client.py 192.168.1.1 2554 > 0 > > What I wanted: > [-]Modulok at modUnix> ./latency_client.py 192.168.1.1 2554 > 0 > 1 > 2 > > > CODE: > ################################ > # The client program: > ################################ > import socket > import sys > def main(): > '''Send data to a server and receive the data echoed back to us.''' > > s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) > s.connect( ('192.168.1.1', 2554) ) > > for i in range(3): > s.sendall(str(i)) > print s.recv(1024) > s.close() > > # Execution starts here: > try: > main() > except KeyboardInterrupt: > sys.exit("Aborting.") > > ################################ > # The server program: > ################################ > import socket > import sys > def main(): > '''Listen for a client and echo data back to them.''' > > s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) > s.bind( ('192.168.1.1', 2554) ) > s.listen(5) > > print "Listening for clients..." > while True: > channel, client = s.accept() > print "Got connection from %s" % client[0] > message = channel.recv(1024) > channel.send(message) > channel.close() > Problem is you close the channel after one string is processed. That in turn closes the client socket. Either keep the channel open or put the client connect in the loop. > # Execution starts here: > try: > main() > except KeyboardInterrupt: > sys.exit("Aborting.") > _______________________________________________ > Tutor maillist - Tutor at python.org > To unsubscribe or change subscription options: > http://mail.python.org/mailman/listinfo/tutor > > -- Bob Gailer 919-636-4239 Chapel Hill NC From amartin7211 at gmail.com Fri Jun 18 19:53:14 2010 From: amartin7211 at gmail.com (Andrew Martin) Date: Fri, 18 Jun 2010 13:53:14 -0400 Subject: [Tutor] pydoc? Message-ID: Hey, everyone, I am new to programming and just downloaded Python 2.6 onto my windows vista laptop. I am attempting to follow 4.11 of the tutorial called "How to Think Like a Computer Scientist: Learning with Python v2nd Edition documentation" ( http://openbookproject.net/thinkcs/python/english2e/ch04.html). However, I am having some trouble. I am trying to use pydoc to search through the python libraries installed on my computer but keep getting an error involving the $ symbol. $ pydoc -g SyntaxError: invalid syntax Can anyone help me out? Thanks -------------- next part -------------- An HTML attachment was scrubbed... URL: From bgailer at gmail.com Fri Jun 18 20:19:23 2010 From: bgailer at gmail.com (bob gailer) Date: Fri, 18 Jun 2010 14:19:23 -0400 Subject: [Tutor] pydoc? In-Reply-To: References: Message-ID: <4C1BB8AB.5070106@gmail.com> On 6/18/2010 1:53 PM, Andrew Martin wrote: > Hey, everyone, I am new to programming and just downloaded Python 2.6 > onto my windows vista laptop. I am attempting to follow 4.11 of the > tutorial called "How to Think Like a Computer Scientist: Learning with > Python v2nd Edition documentation" > (http://openbookproject.net/thinkcs/python/english2e/ch04.html). > However, I am having some trouble. I am trying to use pydoc to search > through the python libraries installed on my computer but keep getting > an error involving the $ symbol. It is good that you keep getting it. Consistency is valuable. > > $ pydoc -g > SyntaxError: invalid syntax Where are you typing this? Where did you get the idea that $ pydoc -g is a valid thing to do? In what way does this relate to the tutorial? What OS are you using? Please learn to ask "good" questions - which in this case means to tell us a lot more about what you are doing. Please also reply-all so a copy of your reply goes to the tutor list. -- Bob Gailer 919-636-4239 Chapel Hill NC From bgailer at gmail.com Fri Jun 18 20:29:11 2010 From: bgailer at gmail.com (bob gailer) Date: Fri, 18 Jun 2010 14:29:11 -0400 Subject: [Tutor] pydoc? In-Reply-To: References: Message-ID: <4C1BBAF7.5070605@gmail.com> On 6/18/2010 1:53 PM, Andrew Martin wrote: > Hey, everyone, I am new to programming and just downloaded Python 2.6 > onto my windows vista laptop. I am attempting to follow 4.11 of the > tutorial called "How to Think Like a Computer Scientist: Learning with > Python v2nd Edition documentation" > (http://openbookproject.net/thinkcs/python/english2e/ch04.html). > However, I am having some trouble. I am trying to use pydoc to search > through the python libraries installed on my computer but keep getting > an error involving the $ symbol. > > $ pydoc -g > SyntaxError: invalid syntax I make a guess - that you are typing $ pydoc -g at the Python Interpreter prompt (>>>) The manual recommends typing it a the shell prompt. In which case the $ represents the prompt and you should just type pydoc -g. -- Bob Gailer 919-636-4239 Chapel Hill NC From lowelltackett at yahoo.com Fri Jun 18 23:42:48 2010 From: lowelltackett at yahoo.com (Lowell Tackett) Date: Fri, 18 Jun 2010 14:42:48 -0700 (PDT) Subject: [Tutor] pydoc? Message-ID: <139671.48213.qm@web110107.mail.gq1.yahoo.com> >From the virtual desk of Lowell Tackett --- On Fri, 6/18/10, Andrew Martin