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Mon Jan 12 10:55:50 EST 2004 · https://mail.python.org/pipermail/python-dev/2004-January/041952.html

Jeremy Hylton <jeremy at alum.mit.edu> writes:

> On Mon, 2004-01-12 at 05:58, Armin Rigo wrote:
>> Sorry to bring this out again, I didn't find a reference about the following 
>> issue in generator expressions:
>> 
>>   (for x in expr)
>> 
>> When should 'expr' be evaluated?  A priori, one would expect it to be 
>> evaluated immediately, but it is not what the suggested implementation does:
>> 
>> def __gen():
>>   for x in expr:
>>     yield x
>> __gen()
>
> First a quick clarification:  Is the "suggested implementation" SF patch
> 872326 or is it that implementation sketch in PEP 289?  The latter
> certainly suggests it, but it's hard to tell even then if it's
> intentional.  Perhaps we should work out the formal specification part
> of the PEP in parallel with the implementation.  The PEP currently says
> that the reference manual should contain a specification, but that spec
> is supposed to be part of the PEP, too.
>
> I agree, at any rate, that the expression should be evaluated
> immediately.  That's easy enough to implement:
>
> def __gen(it):
>     for x in it:
>         yield x
> __gen()

Should be __gen(expr), right?

Cheers,
mwh

-- 
  For their next act, they'll no doubt be buying a firewall 
  running under NT, which makes about as much sense as 
  building a prison out of meringue.                     -- -:Tanuki:-
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[Python-Dev] [872326] generator expression implementation