Incorrect scope of list comprehension variables
no.email at nospam.invalid
Sun Apr 4 23:50:54 CEST 2010
Alain Ketterlin <alain at dpt-info.u-strasbg.fr> writes:
> d[r] = [r for r in [4,5,6]]
> THe problem is that the "r" in d[r] somehow captures the value of the
> "r" in the list comprehension, and somehow kills the loop interator.
Yes, this is a well known design error in Python 2.x. The 3.x series
fixes this error but introduces other errors of its own. It is evil
enough that I almost always use this syntax instead:
d[r] = list(r for r in [4,5,6])
that works in 3.x and the later releases of 2.x. In early 2.x (maybe up
to 2.2) it throws an error at compile time rather than at run time.
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