main.py

# Why not to just put all your code under if __name__ == '__main__':
# (AKA why you should use a main(argv) function)

import sys


def my_func(param):
    print param
    # You'd think this would fail, but it works, because new_param is in the
    # parent level scope. It will fail if you import this file and call
    # my_func, of course.
    print new_param


if __name__ == '__main__':
    # I am adding a new param, so let's unpack it into a new variable
    (param, new_param) = sys.argv[1:2]
    # Here, I should call my func with this exciting new parameter,
    # but I forgot
    my_func(param)