app/django/utils/checksums.py
author Lennard de Rijk <ljvderijk@gmail.com>
Fri, 24 Jul 2009 21:00:04 +0200
changeset 2678 a525a55833f1
parent 54 03e267d67478
permissions -rw-r--r--
Send out a Notification upon creation of a new Request entity. The receivers are specified by the corresponding Role logic this Role Request is for. Currently Organization and Club Administrators will receive "new request" messages about respectively Mentor and Club Membership requests. Fixes Issue 442.

"""
Common checksum routines (used in multiple localflavor/ cases, for example).
"""

__all__ = ['luhn',]

LUHN_ODD_LOOKUP = (0, 2, 4, 6, 8, 1, 3, 5, 7, 9) # sum_of_digits(index * 2)

def luhn(candidate):
    """
    Checks a candidate number for validity according to the Luhn
    algorithm (used in validation of, for example, credit cards).
    Both numeric and string candidates are accepted.
    """
    if not isinstance(candidate, basestring):
        candidate = str(candidate)
    try:
        evens = sum([int(c) for c in candidate[-1::-2]])
        odds = sum([LUHN_ODD_LOOKUP[int(c)] for c in candidate[-2::-2]])
        return ((evens + odds) % 10 == 0)
    except ValueError:  # Raised if an int conversion fails
        return False