app/django/utils/checksums.py
author Lennard de Rijk <ljvderijk@gmail.com>
Fri, 23 Jan 2009 09:08:26 +0000
changeset 913 db38e7680d1c
parent 54 03e267d67478
permissions -rw-r--r--
Added state property to role model. This can be used when for instance a member has been removed from a club or a when a program has been marked inactive. Certain roles would then be shown on the upcoming roles page marked as previous roles. This would give us the archiving capability that was shown in the mockup. Patch by: Lennard de Rijk Reviewd by: to-be-reviewed

"""
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