app/django/utils/checksums.py
author Sverre Rabbelier <srabbelier@gmail.com>
Sat, 22 Nov 2008 13:59:34 +0000
changeset 553 c0cc20b4afc9
parent 54 03e267d67478
permissions -rw-r--r--
Make redirect generic using the new Lists object This makes it possible (and easier) to have the list view redirect to any page specially tailored to the current item. Patch by: Sverre Rabbelier

"""
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