Calling a function with unknown arguments?

Gabriel Genellina gagsl-py2 at yahoo.com.ar
Thu Mar 8 00:21:44 CET 2007


En Wed, 07 Mar 2007 19:55:08 -0300, Rob <crowell at mit.edu> escribió:

> I can get a list of a function's arguments.
>>>> def bob(a, b):
> ...     return a+b
> ...
>>>> bob.func_code.co_varnames
> ('a', 'b')
>
> Let's say that I also have a dictionary of possible arguments for this
> function.
>>>> possible = {'a':10, 'b':5, 'c':-3}
>
> How do I proceed to call bob(a=10, b=5) with this information?

You're almost done. Notice that co_varnames includes local variables too;  
only the first co_argcount are positional arguments.
If you only want to deal with positional arguments (no *args, no **kw):

py> def bob(a,b):
...   c = a+b
...   return c
...
py> bob.func_code.co_varnames
('a', 'b', 'c')
py> bob.func_code.co_argcount
2
py> args = dict((name, possible[name]) for name in  
bob.func_code.co_varnames[:bo
b.func_code.co_argcount] if name in possible)
py> args
{'a': 10, 'b': 5}
py> bob(**args)
15

It can handle missing arguments (if they have a default value, of course):

py> def bob(a, k=3):
...   return a+k
...
py> args = dict((name, possible[name]) for name in  
bob.func_code.co_varnames[:bo
b.func_code.co_argcount] if name in possible)
py> args
{'a': 10}
py> bob(**args)
13

-- 
Gabriel Genellina




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