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From: Gregory Ewing <greg.ewing@canterbury.ac.nz>
Newsgroups: comp.lang.python
Subject: Re: PyEval_GetLocals and unreferenced variables
Date: Thu, 04 Dec 2014 01:28:19 +1300
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Kasper Peeters wrote:
> That may have been the design plan, but in Python 2.7.6, I definitely
> am able to inject locals via PyEval_GetLocals() and have them be visible
> both from the C and Python side;

What seems to be happening is that the dict created by
PyEval_GetLocals() is kept around, so you can change it
and have the changes be visible through locals() in
Python.

However, that doesn't create a local *name* that's
visible from Python. Or if the local name exists,
changes made through locals() aren't reflected in
the value of the local name.

Existing local name is not changed:

 >>> def f():
...  a = 42
...  locals()['a'] = 17
...  print a
...
 >>> f()
42

Can't create a local name:

 >>> def g():
...  locals()['a'] = 17
...  print a
...
 >>> g()
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
   File "<stdin>", line 3, in g
NameError: global name 'a' is not defined

Changes to locals() persist:

 >>> def h():
...  locals()['a'] = 17
...  print locals()['a']
...
 >>> h()
17

-- 
Greg