[Python-Dev] Python3 compiled listcomp can't see local var - bug or feature?

Eric Fahlgren ericfahlgren at gmail.com
Mon Jun 11 18:31:03 EDT 2018

On Mon, Jun 11, 2018 at 3:10 PM Rob Cliffe via Python-Dev <
python-dev at python.org> wrote:

> Skip, I think you have misunderstood the  point I was making.  It was
> not whether the loop variable should leak out of a list comprehension.
> Rather, it was whether a local variable should, so to speak, "leak into"
> a list comprehension.  And the answer is: it depends on whether the code
> is executed normally, or via exec/eval.  Example:
> def Test():
>        x = 1
>        print([x+i for i in range(1,3)])              # Prints [2,3]
>        exec('print([x+i for i in range(1,3)])') # Raises NameError (x)
> Test()
> I (at least at first) found the difference in behaviour surprising.

​Change 'def' to 'class' and run it again.  You'll be even more surprised.​
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