app/django/utils/checksums.py
author Lennard de Rijk <ljvderijk@gmail.com>
Mon, 30 Mar 2009 21:16:18 +0000
changeset 2034 59de158c936d
parent 54 03e267d67478
permissions -rw-r--r--
Fixed the duplicate slots view. The script would not clear the screen upon recalculation also the list of duplicates would increase with every iteration because the variables weren't properly reset. Patch by: Merio Ferraro, 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