Checking for invalid keyword arguments?

Oren Tirosh oren-py-l at
Mon Sep 29 12:42:05 CEST 2003

On Sun, Sep 28, 2003 at 05:06:11PM -0400, Roy Smith wrote:
> I've got a function that takes a couple of optional keyword arguments.  
> I want to check to make sure I didn't get passed an argument I didn't 
> expect.  Right now I'm doing:
>         conversion = None
>         drop = False
>         for key, value in kwArgs.items():
>             if key == 'conversion':
>                 conversion = value
>             elif key == 'drop':
>                 drop = value
>             else:
>                 raise TypeError ('Unexpected keyword argument %s' % key)
> which seems kind of verbose.  Is there a neater way to do this check?

Python's built-in default argument mechanism does exactly that: 

def f(conversion=None, drop=False, ...):

I assume that you have some good reason for using kwargs instead such as 
passing a bunch of arguments together as a dict but you can unpack this 
bunch by calling another function:

def f(**kwargs):
   def f2(conversion=None, drop=False):

   return f2(**kwargs)


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