app/django/utils/checksums.py
author Lennard de Rijk <ljvderijk@gmail.com>
Sun, 08 Mar 2009 13:14:28 +0000
changeset 1741 0da1285f5bc0
parent 54 03e267d67478
permissions -rw-r--r--
Public reviews are now shown on the public page for the student proposal. The assigned mentor name has been removed from the public page. The student proposal view now uses the new getReviewsForEntity method. Patch by: Lennard de Rijk Reviewed 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