Nick Coghlan a écrit :
Python offers two variants on the basic iterative loop.
"for NAME from EXPR:" enforces finalisation of the iterator. At loop completion, a well-behaved iterator is always completely exhausted. This form supports block management operations, that ensure timely release of resources such as locks or file handles.
If the values being iterated over are not required, then the statement may be simplified to "for EXPR:".
"for NAME in EXPR:" skips the finalisation step. At loop completion, a well-behaved iterator may still contain additional values. This form allows an iterator to be consumed in stages.
Regardless of whether you like the above or not, I think the PEP's proposed use of 'as' is incorrect - it looks like the variable should be referring to the expression being iterated over, rather than the values returned from the iterator.
Cheers, Nick.
Well, I would go a step further and keep only the for-loop syntax, mainly because I don't understand why there is two syntax for things that's so close we can merge them !
You can simply states that the for-loop call the "__error__" method of the object if available without invalidating any other property of the new for-loop (ie. as defined in the PEP 340).
One main reason is a common error could be (using the synchronised iterator introduced in the PEP):
for l in synchronised(mylock): do_something()
It will compile, run, never raise any error but the lock will be acquired and never released !
Then, I think there is no use case of a generator with __error__ in the for-loop as it is now. So, IMO, it is error-prone and useless to have two different syntaxes for such things.
Pierre
-- Pierre Barbier de Reuille
INRA - UMR Cirad/Inra/Cnrs/Univ.MontpellierII AMAP Botanique et Bio-informatique de l'Architecture des Plantes TA40/PSII, Boulevard de la Lironde 34398 MONTPELLIER CEDEX 5, France
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