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

There are some errors in your code:

result = divmod(sum_of_digits, 10)

returns a tuple, you need only modulo, that is use

result = sum_of_digits % 10

Second, to check for validity, you don't omit last digit (that is checksum), but include it in computations. Use

reverse_sequence = list(int(d) for d in str(int(number[::-1]))) 

And check for result being zero:

if not result:
    print("[VALID] %s" % number)

Or if you insist on keeping this not needed complexity, check for last digit to be inverse of checksum modulo 10: keep

reverse_sequence = list(int(d) for d in str(int(number[-2::-1])))

but use

if (result + last_digit) % 10 == 0:
    print("[VALID] %s" % number)

For a simplier and shorter code, I can give you a reference to my older answer.