Python garbage collector/memory manager behaving strangely

[Dave Angel]

On 09/17/2012 07:47 AM, Steven D'Aprano wrote:
> On Mon, 17 Sep 2012 06:46:55 -0400, Dave Angel wrote:
>
>> On 09/16/2012 11:25 PM, alex23 wrote:
>>>     def readlines(f):
>>>         lines = []
>>>         while "f is not empty":
>>>             line = f.readline()
>>>             if not line: break
>>>             if len(line) > 2 and line[-2:] == '|\n':
>>>                 lines.append(line)
>>>                 yield ''.join(lines)
>>>                 lines = []
>>>             else:
>>>                 lines.append(line)
>> There's a few changes I'd make:
>> I'd change the name to something else, so as not to shadow the built-in,
> Which built-in are you referring to? There is no readlines built-in.
>
> py> readlines
> Traceback (most recent call last):
>   File "<stdin>", line 1, in <module>
> NameError: name 'readlines' is not defined
>
>
> There is a file.readlines method, but that lives in a different namespace 
> to the function readlines so there should be no confusion. At least not 
> for a moderately experienced programmer, beginners can be confused by the 
> littlest things sometimes.

You're right of course, and that's not restricted to beginners.  I've
been at this for over 40 years, and I make that kind of mistake once in
a while.  Fortunately, when I make such a mistake on this forum, you
usually pop in to keep me honest.  When I make it in code, I either get
a runtime error, or no harm is done.

>
>> and to make it clear in caller's code that it's not the built-in one.
>> I'd replace that compound if statement with
>>       if line.endswith("|\n":
>> I'd add a comment saying that partial lines at the end of file are
>> ignored.
> Or fix the generator so that it doesn't ignore partial lines, or raises 
> an exception, whichever is more appropriate.
>
>
>


-- 

DaveA