app/django/utils/checksums.py
author Madhusudan C.S. <madhusudancs@gmail.com>
Tue, 11 Aug 2009 12:48:10 -0700
changeset 2757 7d0d0ce76bd9
parent 54 03e267d67478
permissions -rw-r--r--
updateOrCreateFromFields is made to call updateOrCreateFromKeyName. updateOrCreateFromFields called self._model.get_or_insert which only creates new entities but doesn't update the properties if the entity already exists. So updateOrCreateFromFields is now made to call updateOrCreateFromKeyName which actually updates the entity properties if entity already exists. 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