Python decorator that ignores unneeded keyword arguments

ignore_unused_args.py

import inspect

def ignore_unused_args(f):
    arg_spec = inspect.getargspec(f)
    def new_f(*args, **kwargs):
        new_kwargs = {key:kwargs[key] for key in arg_spec.args if key in kwargs}
        return f(*args, **new_kwargs)
    new_f.spec = arg_spec
    return new_f

# Example Usage
@ignore_unused_args
def fn_1(a, b, c=100):
    print a,b,c

fn_1(a=1, b=2, c=3, d=4)
# Prints "1 2 3"
# Without the decorator, it would give an error:
#   TypeError: fn_1() got an unexpected keyword argument 'd'