Checking the card number using the Luhn algorithm. Test it.

Neat script, I've tested it and as far as I can tell it works just fine. I don't have anything to note in regard to the code itself. I'm not really sure in what sense you could improve the code besides following the 'pep8 style guide' on the python website (not necessary, but recommended). pep8 style guide: https://www.python.org/dev/peps/pep-0008/