app/django/utils/checksums.py
author Madhusudan C.S. <madhusudancs@gmail.com>
Fri, 05 Jun 2009 21:27:03 +0200
changeset 2397 d943fa182fae
parent 54 03e267d67478
permissions -rw-r--r--
Moved the GHOP module into the modules package. This also includes moving the templates and content into their respective place inside the Soc folder. This is to avoid adding every folder to the app.yaml file. Patch by: Madhusudan C.S. and Lennard de Rijk Reviewed by: Lennard de Rijk

"""
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