generator expression works in shell, NameError in script

guthrie grguthrie at gmail.com
Sun Jun 21 18:00:52 CEST 2009


On Jun 18, 11:28 pm, greg <g... at cosc.canterbury.ac.nz> wrote:
> nn wrote:
> > This is certainly an odd one. This code works fine under 2.6 but fails
> > in Python 3.1.
>
> >>>>class x:
>
> > ...     lst=[2]
> > ...     gen=[lst.index(e) for e in lst]
>
> In 3.x it was decided that the loop variables in a list
> comprehension should be local, and not leak into the
> surrounding scope. This was implemented by making the
> list comprehension into a nested function.
>
> Unfortunately this leads to the same unintuitive
> behaviour as a genexp when used in a class scope.
>
-- I don't get this - the only local loop variable is "e", not lst.
And lst is used twice in the generator expression, which is being
complained about?

It would generally be the case that a nested function would have
access to its enclosing scope.

In any case, even if/when the current behavior is explained or
rationalized, it certainly appears un-intuitive, and that is another
level of "error"! :-)



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