app/django/utils/checksums.py
author Lennard de Rijk <ljvderijk@gmail.com>
Tue, 07 Apr 2009 21:40:23 +0000
changeset 2121 4f6344dfab28
parent 54 03e267d67478
permissions -rw-r--r--
Added list of projects to the organization home page. Only projects that have not failed will be shown here. The list will link to each project public page which will contain the necessary info about the project. Addresses part of Issue 491. Patch by: Madhusudan C.S 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