Question about name scope

Ian Kelly ian.g.kelly at gmail.com
Wed Feb 1 23:38:17 CET 2012


On Wed, Feb 1, 2012 at 3:24 PM, Ethan Furman <ethan at stoneleaf.us> wrote:
> Definitely should rely on it, because in CPython 3 exec does not un-optimize
> the function and assigning to locals() will not actually change the
> functions variables.

Well, the former is not surprising, since exec was changed from a
statement to a built-in.  I don't see any difference in the way
locals() behaves, though:

Python 3.2 (r32:88445, Feb 20 2011, 21:29:02) [MSC v.1500 32 bit (Intel)] on win
32
Type "help", "copyright", "credits" or "license" for more information.
>>> def f(x, y):
...     locals()[x] = y
...     print(vars())
...     exec('print(' + x + ')')
...
>>> f('a', 42)
{'y': 42, 'x': 'a', 'a': 42}
42

That still seems to work as I described it.  You couldn't directly
reference it as 'a', though, since the result would be either that it
would try to look up a global with that name, or the compiler would
consider it a local, optimize it, and then you could no longer assign
it via locals().

Cheers,
Ian



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