Implementation of Luhn Formula

Question

I was trying to implement the Luhn Formula in Python. Here is my code:

import sys


def luhn_check(number):
    if number.isdigit():
        last_digit = int(         


        

Answer 1

I think the algorithm is not correct.

The second step you need to sum the digits of the products instead of substract 9. Reference: Wikipedia.

In the Wikipedia you have this example:

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(4532015112830366)
print 'Correct:' + str(result)
result = is_luhn_valid(6011514433546201)
print 'Correct:' + str(result)
result = is_luhn_valid(6771549495586802)
print 'Correct:' + str(result)

Result:

>>>Correct:True
>>>Correct:True
>>>Correct:True