app/django/utils/checksums.py
author Pawel Solyga <Pawel.Solyga@gmail.com>
Sun, 24 May 2009 22:29:54 +0200
changeset 2335 366e64ecba91
parent 54 03e267d67478
permissions -rw-r--r--
Add web based python shell to Melange. It is accessible via http://host/admin/shell url and requires developer rights. Shell project is part of google-app-engine-samples. This commit moves django configuration from main.py to separate gae_django.py module. Shell project has been modified in order to work correctly with django 1.0+. Build script has been updated and includes shell folder and gae_django.py file. http://code.google.com/p/google-app-engine-samples/source/browse/trunk/shell/

"""
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