Supply condition in function call

[Chris Angelico]

On Fri, Mar 27, 2015 at 12:41 PM, Rustom Mody <rustompmody at gmail.com> wrote:
> On Thursday, March 26, 2015 at 11:30:57 AM UTC+5:30, Chris Angelico wrote:
>> On Thu, Mar 26, 2015 at 3:02 PM, Rustom Mody  wrote:
>> > [And BTW
>> > help(filter) in python2 is much better documention than in python3
>> > ]
>>
>> Python 2.7.3 (default, Mar 13 2014, 11:03:55)
>> [GCC 4.7.2] on linux2
>>
>> filter(...)
>>     filter(function or None, sequence) -> list, tuple, or string
>>
>>     Return those items of sequence for which function(item) is true.  If
>>     function is None, return the items that are true.  If sequence is a tuple
>>     or string, return the same type, else return a list.
>>
>> Python 3.5.0a0 (default:4709290253e3, Jan 20 2015, 21:48:07)
>> [GCC 4.7.2] on linux
>>
>> class filter(object)
>>  |  filter(function or None, iterable) --> filter object
>>  |
>>  |  Return an iterator yielding those items of iterable for which function(item)
>>  |  is true. If function is None, return the items that are true.
>>  |
>>  |  Methods defined here:
>> (chomp a handful of method details)
>
> Sackful may be more accurate :-)

Not really. Here's the entire help(filter) text:

Help on class filter in module builtins:

class filter(object)
 |  filter(function or None, iterable) --> filter object
 |
 |  Return an iterator yielding those items of iterable for which function(item)
 |  is true. If function is None, return the items that are true.
 |
 |  Methods defined here:
 |
 |  __getattribute__(self, name, /)
 |      Return getattr(self, name).
 |
 |  __iter__(self, /)
 |      Implement iter(self).
 |
 |  __new__(*args, **kwargs) from builtins.type
 |      Create and return a new object.  See help(type) for accurate signature.
 |
 |  __next__(self, /)
 |      Implement next(self).
 |
 |  __reduce__(...)
 |      Return state information for pickling.


> On a different note... I wonder how you do it:
> Look at 300 lines of code and notice exactly those 3 that... um... cause
> a lot of trouble :-)
> [My eyes just glaze over]

That's called experience. It's an intrinsic part of being a programmer.

> On a more specific note, its the 1st line:
>
> class filter(object)
>
> which knocks me off.
> If a more restricted type from the ABC was shown which exactly captures all
> the iterator-specific stuff like __iter__, __next__ it would sure help (me)

But there's no point in subclassing for everything. In this case,
filter doesn't subclass anything but object, so there's no value in
stating anything else. You want to know if it's iterable? Check for an
__iter__ method. Etcetera.

> On a 3rd note: I think Ive found a little buglet while trying to post this message, can you confirm?
> [Linux Debian Xfce]
>
> After selecting the line above [inside python inside help(filter) ]for
> cut-pasting here, by mistake I pressed Ctrl-C rather than Ctrl-Shift-C
> An exception was thrown and the terminal remained in some sort of raw mode
> even after exiting python

Yes, confirmed. It'll be something to do with what happens when you
have 'less' and readline working together, probably.

Tip: Use Ctrl-Insert rather than Ctrl-Shift-C. It's the more standard
keystroke anyway.

ChrisA