app/django/utils/checksums.py
author Lennard de Rijk <ljvderijk@gmail.com>
Tue, 03 Feb 2009 08:25:47 +0000
changeset 1195 cbef45d75942
parent 54 03e267d67478
permissions -rw-r--r--
Fixed a bug where a GMAP error message would be displayed when the form was not valid. The wrong params were used, so the wrong template was used to display the form. This also caused the instruction_text to dissapear. 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