passing a custom locals to a function

[Steven Taschuk]

Quoth Kuzminski, Stefan R:
> I'm trying to allow for variables in a dictionary to be manipulated
> directly ( without specifying the dictionary ) by putting the values in
> the local namespace. The end result for the users of the tool I'm
> creating is that they can fill in the body of the 'work' function below
> with more natural syntax ( var1 + var2 rather than dict['var1'] +
> dict['var2]  )
  [...]
> This works but is too slow ( and is a bit of a kludge getting the locals
> back into the dict because of extra things that might be in locals I
> don't want in the dict such as self ).  I tried to eval and exec passing
> locals explicitly, but if I point exec to a function, the locals don't
> seem to show up inside the function..

As Alex explained, fiddling with the locals of a function will be
difficult.

You could instead consider the user's code to be a module rather
than the body of a function, and use your dict for the globals in
that module.  That is, let your users write a file such as
    # userfile.py
    a, b = a+b, a
and then invoke it with
    >>> vars = {'a': 8, 'b': 5}
    >>> execfile('userfile.py', vars)
    >>> del vars['__builtins__']
    >>> vars
    {'a': 13, 'b': 8}
or
    >>> source = file('userfile.py').read()
    >>> exec source in vars
    >>> del vars['__builtins__']
    >>> vars
    {'a': 21, 'b': 13}
or some such.

-- 
Steven Taschuk                staschuk at telusplanet.net
"I tried to be pleasant and accommodating, but my head
 began to hurt from his banality."   -- _Seven_ (1996)