[Python-Dev] PEP for Better Control of Nested Lexical Scopes (original) (raw)

Greg Ewing greg.ewing at canterbury.ac.nz
Thu Feb 23 05:25:30 CET 2006

Samuele Pedroni wrote:

If you are looking for rough edges about nested scopes in Python this is probably worse:

>>> x = [] >>> for i in range(10): ... x.append(lambda : i) ... >>> [y() for y in x] [9, 9, 9, 9, 9, 9, 9, 9, 9, 9]

As an aside, is there any chance that this could be changed in 3.0? I.e. have the for-loop create a new binding for the loop variable on each iteration.

I know Guido seems to be attached to the idea of being able to use the value of the loop variable after the loop exits, but I find that to be a dubious practice readability-wise, and I can't remember ever using it. There are other ways of getting the same effect, e.g. assigning it to another variable before breaking out of the loop, or putting the loop in a function and using return.

-- Greg Ewing, Computer Science Dept, +--------------------------------------+ University of Canterbury, | Carpe post meridiam! | Christchurch, New Zealand | (I'm not a morning person.) | greg.ewing at canterbury.ac.nz +--------------------------------------+

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