modifying vars() dictionary?

[Alex]

> In the documentation, it says about vars():
> 
>     The returned dictionary should not be modified: the effects on the
>     corresponding symbol table are undefined.
> 
> Why are the effects undefined?  Why doesn't it always work to set a
> value for variable 'x' by assigning that value to the 'x' element of
> the dictionary from vars()?

Well... it just is.  You could have a look at the source code. :)

Why do you want to do this?

Alex.