Incorrect scope of list comprehension variables
apt.shansen at gmail.invalid
Sun Apr 4 20:42:08 EDT 2010
On 2010-04-04 14:50:54 -0700, Paul Rubin said:
> 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.
I have a dramatic suggestion.
Why not use this syntax:
d[r] = [something_else for something_else in [4,5,6]]
Where something_else is basically any conceivable name in the whole
wide world which does not have meaning in the current local scope.
Just for clarity's sake, not sharing names is swell.
... p.s: change the ".invalid" to ".com" in email address to reply privately.
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