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Date: Tue, 18 Sep 2012 23:51:13 +0200
From: Thomas Jollans <t@jollybox.de>
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To: python-list@python.org
Subject: Re: User defined lexical scoping... can I do this?
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Xref: csiph.com comp.lang.python:29453

On 09/18/2012 10:50 PM, weissman.mark@gmail.com wrote:
> Well there's wired stuff like this:
> 
> In [1]: locals()["x"] = 5
> 
> In [2]: print x
> 5
> 

No, there isn't. Modifying the dictionary returned by locals() has no
effect.

>>> def f ():
...     locals()["x"] = 1
...     return x
...
>>> f ()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 3, in f
NameError: global name 'x' is not defined
>>>
>>> locals()["x"] = 1
>>> x
1
>>> #this works because
... locals() is globals()
True
>>>

The exception is the case when local scope is identical to global scope.
In this case, locals() has globals() semantics.