defining the behavior of zip(it, it) (WAS: Converting a flatlist...)

[bonono at gmail.com]

yet another :-)

Fredrik Lundh wrote:
> Steven Bethard wrote:
>
> > Then why document itertools.izip() as it is?  The documentation there is
> > explicit enough to know that izip(it, it) will work as intended.  Should
> > we make the documentation there less explicit to discourage people from
> > using the izip(it, it) idiom?
>
> depends on whether you interpret "equivalent" as "having similar effects"
> or "corresponding or virtually identical especially in effect or function" or
> if you prefer some other dictionary definition...
>
> because there are of course plenty of subtle differences between a Python
> generator C type implementation.  let's see...
>
> >>> from itertools import izip as izip1
> >>> from library documentation import izip as izip2
>
> >>> izip1
> <type 'itertools.izip'>
> >>> izip2
> <function izip2 at 0x00A26670>
>
> alright, close enough.
>
> >>> izip1.func_name
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> AttributeError: type object 'itertools.izip' has no attribute 'func_name'
> >>> izip2.func_name
> 'izip'
>
> hmm.
>
> >>> class myiter:
> ...     def next(self):
> ...             raise ValueError("oops!")
> ...
> >>> izip2(myiter())
> <generator object at 0x00A2AB48>
> >>> izip1(myiter())
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
> TypeError: izip argument #1 must support iteration
>
> oops.
>
> >>> class myiter:
> ...     def __iter__(self):
> ...             return self
> ...     def next(self):
> ...             raise ValueError("oops!")
> ...
> >>> izip1(myiter())
> <itertools.izip object at 0x00A2AC88>
> >>> izip2(myiter())
> <generator object at 0x00A2AB48>
>
> that's better.  now let's run it:
>
> >>> list(izip1(myiter()))
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
>   File "<stdin>", line 5, in next
> ValueError: oops!
> >>> list(izip2(myiter()))
> Traceback (most recent call last):
>   File "<stdin>", line 1, in ?
>   File "i.py", line 6, in izip2
>     result = [i.next() for i in iterables]
>   File "<stdin>", line 5, in next
> ValueError: oops!
>
> different stack depths.  hmm.
> 
> so how equivalent must something be to be equivalent?
> 
> </F>