/bangkokhotel/lib/python2.5/site-packages/django/utils/checksums.py

https://bitbucket.org/luisrodriguez/bangkokhotel · Python · 22 lines · 11 code · 3 blank · 8 comment · 5 complexity · 55675dafc05a3857ee55a42bbddf7654 MD5 · raw file

  1. """
  2. Common checksum routines (used in multiple localflavor/ cases, for example).
  3. """
  4. __all__ = ['luhn',]
  5. LUHN_ODD_LOOKUP = (0, 2, 4, 6, 8, 1, 3, 5, 7, 9) # sum_of_digits(index * 2)
  6. def luhn(candidate):
  7. """
  8. Checks a candidate number for validity according to the Luhn
  9. algorithm (used in validation of, for example, credit cards).
  10. Both numeric and string candidates are accepted.
  11. """
  12. if not isinstance(candidate, basestring):
  13. candidate = str(candidate)
  14. try:
  15. evens = sum([int(c) for c in candidate[-1::-2]])
  16. odds = sum([LUHN_ODD_LOOKUP[int(c)] for c in candidate[-2::-2]])
  17. return ((evens + odds) % 10 == 0)
  18. except ValueError: # Raised if an int conversion fails
  19. return False