Validate routing number in Python

validate_routing_number.py

"""
The function checks correctness of a routing number using the Checksum algorithm.
Checksum algorithm: http://en.wikipedia.org/wiki/Routing_transit_number#Check_digit
"""
def validate(routing_number):
  if len(s) != 9:
    return False

  n = 0
  for i in xrange(0, len(s), 3):
    n += int(s[i]) * 3
    n += int(s[i + 1]) * 7
    n += int(s[i + 2])

  if n != 0 and n % 10 == 0:
    return True
  else:
    return False

Nitpicky but how about swapping:

if n != 0 and n % 10 == 0:
  return True
else:
  return False

for
return n != 0 and n % 10 == 0

ofcourse, more pythonic :)