app/django/utils/checksums.py
author Pawel Solyga <Pawel.Solyga@gmail.com>
Sun, 08 Mar 2009 00:00:13 +0000
changeset 1731 254375a57d62
parent 54 03e267d67478
permissions -rw-r--r--
Add json2.js to repository under json folder, update build script and app.yaml.template files. This is pretty useful set of functions for JSON manipulation in Javascript, we will mostly use stringify function. This code is on Public Domain license and comes from http://www.json.org/js.html. 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