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

The following might help some people to start with the Luhn algorithm in python.

num = list(input("Please enter the number to test (no space, no symbols, only \
numbers): "))

num = list(map(int, num))[::-1] #let's transform string into int and reverse it

for index in range(1,len(num),2):
    if num[index]<5:
        num[index] = num[index] *2
    else: #doubling number>=5 will give a 2 digit number
        num[index] = ((num[index]*2)//10) + ((num[index]*2)%10)

checksum=sum(num)

print("checksum= {}".format(checksum))

if checksum%10 !=0:
    print('the number is not valid')
else:
    print('the number is valid!')