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Re: Question about name scope

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Ian Kelly wrote:
> On Wed, Feb 1, 2012 at 3:24 PM, Ethan Furman <ethan@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

--> def f(x, y):
...     locals()[x] = y
...     print(vars())
...     exec('print (' + x + ')')
...     print(x)
...
--> f('a', 42)
{'y': 42, 'x': 'a', 'a': 42}
42
a

Indeed -- the point to keep in mind is that locals() can become out of 
sync with the functions actual variables.  Definitely falls in the camp 
of "if you don't know *exactly* what you are doing, do not play this way!"

~Ethan~

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Thread

Question about name scope Olive <diolu@bigfoot.com> - 2012-02-01 18:11 +0100
  Re: Question about name scope Rick Johnson <rantingrickjohnson@gmail.com> - 2012-02-01 09:21 -0800
  Re: Question about name scope Ethan Furman <ethan@stoneleaf.us> - 2012-02-01 09:43 -0800
  Re: Question about name scope Dave Angel <d@davea.name> - 2012-02-01 12:36 -0500
    Re: Question about name scope Mel Wilson <mwilson@the-wire.com> - 2012-02-01 13:47 -0500
      Re: Question about name scope Ian Kelly <ian.g.kelly@gmail.com> - 2012-02-01 14:49 -0700
      Re: Question about name scope Ian Kelly <ian.g.kelly@gmail.com> - 2012-02-01 15:38 -0700
      Re: Question about name scope Ethan Furman <ethan@stoneleaf.us> - 2012-02-01 14:24 -0800
      Re: Question about name scope Ian Kelly <ian.g.kelly@gmail.com> - 2012-02-01 16:00 -0700
      Re: Question about name scope Ethan Furman <ethan@stoneleaf.us> - 2012-02-01 15:08 -0800
      Re: Question about name scope Ian Kelly <ian.g.kelly@gmail.com> - 2012-02-01 16:47 -0700
      Re: Question about name scope Ethan Furman <ethan@stoneleaf.us> - 2012-02-01 14:53 -0800
        Re: Question about name scope Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2012-02-02 00:34 +0000
      Re: Question about name scope Ethan Furman <ethan@stoneleaf.us> - 2012-02-01 15:59 -0800
      Re: Question about name scope Ethan Furman <ethan@stoneleaf.us> - 2012-02-01 15:41 -0800
      Re: Question about name scope Ethan Furman <ethan@stoneleaf.us> - 2012-02-01 15:51 -0800
  Re: Question about name scope Chris Rebert <clp2@rebertia.com> - 2012-02-01 09:38 -0800
  Re: Question about name scope Christian Heimes <lists@cheimes.de> - 2012-02-01 18:50 +0100

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