Generator Comprehensions

Just van Rossum just at xs4all.nl
Tue Jan 29 16:21:41 CET 2002


Skip Montanaro wrote:

>     >> It has always bothered me that the temporary variables inside list
>     >> comprehensions are still visible afterwards (and overwrite existing
>     >> variables):
> 
>     Jason> Wow.  I wasn't aware of that.  But now that I am, it bothers me.
> 
> I don't see any spurious locals:
> 
>     >>> def f(n):
>     ...   l = [i for i in range(n)]
>     ...   print locals()
>     ...   return l
>     ...
>     >>> f(5)
>     {'i': 4, 'l': [0, 1, 2, 3, 4], 'n': 5}
>     [0, 1, 2, 3, 4]
> 
> When you disassemble the function you see a strange local named "_[1]":
> [ ...schnipp... ]

It's not about "_[1]", but about "i": it's not completely obvious (to me at
least) that names used in the comprehension should be part of the local scope.
It doesn't bother me a *lot* that they are, but at the same time I don't see
any use for it either.

Just



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