The Python Apprentice

Accepting command line arguments

That last change actually breaks our main() since it's not passing the new url argument. When running our module as a standalone program, we'll need to accept the URL as a command line argument. Access to command line arguments in Python is through an attribute of the sys module called argv which is a list of strings. To use it we must first import the sys module at the top of our program:

import sys

We then get the second argument (with an index of one) from the list:

def main():    url = sys.argv[1]    words = fetch_words(url)    print_items(words)

And of course this works as expected:

$ python3 words.py http://sixty-north.com/c/t.txtItwasthebestoftimes

This looks fine until we realize that we can't usefully test ...