LuhnAlgorithm.py

#LUHN ALGORITHM
#The Luhn algorithm is as follows:
#From the right to left, double the value of every second digit; if the product is greater than 9, sum the digits of the products.
#Take the sum of all the digits.
#If the sum of all the digits is a multiple of 10, then the number is valid; else it is not valid.
def verify_card_number(card_number):
 sum_of_odd_digits = 0
 card_number_reversed = card_number[::-1]
 odd_digits = card_number_reversed[::2]

 for digit in odd_digits:
 sum_of_odd_digits += int(digit)

 sum_of_even_digits = 0
 even_digits = card_number_reversed[1::2]
 for digit in even_digits:
 number = int(digit) * 2
 if number >= 10:
 number = (number // 10) + (number % 10)
 sum_of_even_digits += number
 total = sum_of_odd_digits + sum_of_even_digits
 return total % 10 == 0

def main():
 card_number = '4111-1111-4555-1142'
 card_translation = str.maketrans({'-': '', ' ': ''})
 translated_card_number = card_number.translate(card_translation)

 if verify_card_number(translated_card_number):
 print('VALID!')
 else:
 print('INVALID!')

main()