luhn.py

import unittest

def luhn_checksum(card_number):
	
    def digits_of(n):
        return [int(d) for d in str(n)]
        
    digits = digits_of(card_number)
    odd_digits = digits[-1::-2]
    even_digits = digits[-2::-2]
    checksum = 0
    checksum += sum(odd_digits)
    
    for d in even_digits:
        checksum += sum(digits_of(d*2))
    return checksum % 10




def is_luhn_valid(card_number):
    return luhn_checksum(card_number) == 0


#result = is_luhn_valid(1800905433149)
#print ("Correct:" + str(result))


#result = is_luhn_valid(6011514433546201)
#print ("Correct:" + str(result))


#result = is_luhn_valid(6771549495586802)
#print ("Correct:" + str(result))
#assert str(result) == 'True', 'should be True'