Get credit card type by number

gistfile1.py

import re


def credit_card_type(number):
    """
    Return a string that represents the type of the credit card number.

    Criteria:
        AMEX: Starts with 34 or 37 and the length 15.
        MASTERCARD: Starts with 51-55 and the length is 16.
        VISA: Starts with 4 and the length is 13 or 16.
        DINNERSCLUB: Starts with 300-306 and the length is 14.
        ENROUTE: Starts with 2014 or 2149 and the length is 15.
        DISCOVER: Starts with 6011 and the length is 16.

    If the number don't match with any criteria return None.
    Inspired in this script: http://javascript.gakaa.com/credit-card-type-by-number.aspx
    """
    number = re.sub(r'\s', '', number)

    def tsrange(*args):
        """Returns a tuple of string"""
        return tuple(map(str, range(*args)))

    known_cards = [['AMEX', ('34', '37'), [15]],
                   ['MASTERCARD', tsrange(51, 56), [16]],
                   ['VISA', ('4'), [13, 16]],
                   ['DINNERSCLUB', tsrange(300, 306), [14]],
                   ['ENROUTE', ('2014', '2149'), [15]],
                   ['DISCOVER', ('6011'), [16]],
                   ['JCB', ('3'), [16]],
                   ['JCB', ('2131', '1800'), [15]]]

    for card_type, starts, length in known_cards:
        if number.startswith(starts) and len(number) in length:
            return card_type

    return None