Help with Python Grammar change

[Travis Oliphant]

I have a question for people familiar with the Python Grammar:

How difficult would it be and what are the problems with altering the
grammar (and compile.c code) so that one can enter slice-syntax as an
argument to a function call:

In other words if g is a function:

def g(a,b):
    # some nifty code
    return

I want

>>> g(1:10:2,3) 

to call function g with slice(1,10,2) and 3 as arguments.

Is this at all possible, or would it break things horribly?

Thanks for any feedback,

Travis Oliphant