app/django/utils/checksums.py
author Matthew Wilkes <matthew@matthewwilkes.co.uk>
Fri, 15 May 2009 15:29:41 +0200
changeset 2314 0a0e603215d7
parent 54 03e267d67478
permissions -rw-r--r--
Include required antl3 library and check if datastore is available The datastore is checked for availability before requesting it to be cleared. This is because gaeftest uses its own method for ensuring no leakage of data by providing a temporary file as the backend. Reviewed by: Sverre Rabbelier

"""
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