app/django/utils/checksums.py
author Pawel Solyga <Pawel.Solyga@gmail.com>
Sun, 19 Oct 2008 21:12:08 +0000
changeset 394 4c60652a3947
parent 54 03e267d67478
permissions -rw-r--r--
Add BaseForm class to soc.views.helper.forms module (work in progress). This changes the way as_table function displays the form (for more information have a look into doc string). BaseForm is going to be used for all forms in Melange in future. Right now it's still missing custom form errors labels and "required" text in 3rd column, but that's added as TODO and I'm working on it. Patch by: Pawel Solyga Review 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