app/django/utils/checksums.py
author Pawel Solyga <Pawel.Solyga@gmail.com>
Wed, 18 Mar 2009 12:41:59 +0000
changeset 1920 0eba9cb1b331
parent 54 03e267d67478
permissions -rw-r--r--
Change the order of student proposals lists for org admins and mentors. Now the new proposals list shows up at the top. Also don't show the list of new proposals if it's empty. Patch by: Pawel Solyga 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