modifying locals

[Steven D'Aprano]

On Fri, 31 Oct 2008 07:10:05 +0100, Tino Wildenhain wrote:

> Also, locals() already returns a dict, no need for the exec trickery.
> You can just modify it:
> 
>  >>> locals()["foo"]="bar"
>  >>> foo
> 'bar'
>

That is incorrect. People often try modifying locals() in the global 
scope, and then get bitten when it doesn't work in a function or class.


>>> def foo():
...     x = 1
...     locals()['y'] = 2
...     y
...
>>> foo()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 4, in foo
NameError: global name 'y' is not defined

You cannot modify locals() and have it work. The fact that it happens to 
work when locals() == globals() is probably an accident.



-- 
Steven