modifying locals

[Steve Holden]

John [H2O] wrote:
> I would like to write a function to write variables to a file and modify a
> few 'counters'. This is to replace multiple instances of identical code in a
> module I am writing. 
> 
> This is my approach:
> 
> def write_vars(D):
>     """ pass D=locals() to this function... """
>     for key in D.keys():
>         exec("%s = %s" % (key,D[key]))
> 
Note that this code will likely fail to execute if D[key] is some object
whose str() method does not return a valid Python expression.

>     outfile.write(...)
>     numcount += 1
>     do this, do that...
> 
> the issue is that at the end, I want to return outfile, numcount, etc... but
> I would prefer to not return them explicitly, that is, I would just like
> that the modified values are reflected in the script. How do I do this?
> Using global? But that seems a bit dangerous since I am using exec.
> 
Return them as a tuple, using an unpacking assignment to bind the
different elements to different names.

> Bringing up another matter... is there a better way to do this that doesn't
> use exec?
> 
It's not really obvious why you are trying to replicate the caller's
namespace inside this function. Perhaps you could explain a little more
what you are trying to achieve.

regards
 Steve
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