[Python-Dev] [872326] generator expression implementation (original) (raw)

Michael Hudson mwh at python.net
Mon Jan 12 10:55:50 EST 2004

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

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