[Tutor] Working with lines from file and printing to another keeping sequential order

[Dan Liang]

Hi Bob, Shantanoo, Kent, and tutors,

Thank you Bob, Shantanoo, Kent for all the nice feedback. Exception
handling, the concept of states in cs, and the use of the for loop with
offset helped a lot. Here is the code I now have, based on your suggestions,
and it does what I need:

ListLines = [ line.rstrip() for line in open('test.txt') ]

countYes = 0
countNo = 0

for i in range(len(ListLines)):
 if ListLines[i].endswith('yes'):
     countYes+=1
     print "countYes", countYes, "\t\t", ListLines[i]

 if not ListLines[i].endswith('yes'):
    continue

 for offset in (1, 2, 3, 4, 5, 6, 7, 8):
    if i+offset < len(ListLines) and ListLines[i+offset].endswith('no'):

       countNo+=1

       print "countNo", countNo, "\t\t", ListLines[i+offset]

Thank you again!

--dan





On Sun, Apr 26, 2009 at 10:55 AM, Kent Johnson <kent37 at tds.net> wrote:

> On Sat, Apr 25, 2009 at 2:11 PM, Dan Liang <danliang20 at gmail.com> wrote:
> > Hi Bob and tutors,
> >
> > Thanks Bob for your response! currently I have the current code, but it
> does
> > not work:
> >
> > ListLines= []
> > for line in open('test.txt'):
> >     line = line.rstrip()
> >     ListLines.append(line)
>
> This could be written with a list comprehension:
> ListLines = [ line.rstrip() for line in open('test.txt') ]
>
> >
> > for i in range(len(ListLines)):
> >
> >     if ListLines[i].endswith("yes") and ListLines[i+1].endswith("no") and
> > ListLines[i+1].endswith("no"):
> >         print ListLines[i], ListLines[i+1], ListLines[i+2]
> >     elif ListLines[i].endswith("yes") and ListLines[i+1].endswith("no"):
> >         print ListLines[i], ListLines[i+1]
> >         elif ListLines[i].endswith("yes"):
> >         print ListLines[i]
> >     elif ListLines[i].endswith("no"):
> >         continue
> >     else:
> >         break
>
> You only need to test for ListLines[i].endswith('yes') once. Then you
> could use a loop to test for lines ending with 'no'.
>
> for i in range(len(ListLines)):
>   if not ListLines[i].endswith('yes'):
>    continue
>  for offset in (1, 2):
>    if i+offset < len(ListLines) and ListLines[i+offset].endswith('no'):
>      print ListLines[i+offset]
>
> You could adapt the above for a variable number of 'no' lines with
> something like
>  for offset in range(1, maxNo+1):
>
> > I get the following error:
> > Traceback (most recent call last):
> >   File "test.py", line 18, in <module>
> >     if ListLines[i].endswith("yes") and ListLines[i+1].endswith("no") and
> > ListLines[i+1].endswith("no"):
> > IndexError: list index out of range
>
> That is because you have a 'yes' line at the end of the file so the
> check for 'no' tries to read past the end of ListLines. In my code the
> test for i+offset < len(ListLines) will prevent that exception.
>
> Kent
>
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