luhn algorithm code example

Example 1: luhn's algorithm python

#Better
#This is the shorter Luhn's algorithm with step-by-step instructions

#Function to split a string into a list of all its constituent characters
def split_char(number_string):
    return [char for char in number_string]

#Function to convert a string list to an integer list
def list_str_to_int(test_list):
    for i in range(0, len(test_list)):
        test_list[i] = int(test_list[i])
    return test_list

#Function to convert an integer list to a string list
def list_int_to_str(test_list):
    for i in range(0, len(test_list)):
        test_list[i] = str(test_list[i])
    return test_list

#Function to multiply all elements of a list by 2
def list_multiplied_by_2(test_list):
    for i in range(0, len(test_list)):
        test_list[i] *= 2
    return test_list

#Prompt the user for Input
ccn = int(input("Enter your digital card number: "))

ccn = str(ccn)

#Specifying a condition to exit the loop
if 12 > len(ccn) < 17:
    print("INVALID")
    exit()

num1 = " " + "".join(ccn[::-1])
num2 = "".join(ccn[::-1])
num3 = "".join(num1[::2])
num4 = "".join(num2[::2])

alternate_num3 = num3.replace(" ", "")

sep1 = split_char(alternate_num3)
sep2 = split_char(num4)

str_to_int1 = list_str_to_int(sep1)
str_to_int2 = list_str_to_int(sep2)

str_2_1 = list_multiplied_by_2(str_to_int1)

int_to_str1 = list_int_to_str(str_2_1)
sep_digits1 = ""
for i in int_to_str1:
    sep_digits1 += "".join(i)

sep3 = split_char(sep_digits1)

str_to_int3 = list_str_to_int(sep3)
sum_last_add1 = sum(str_to_int3)

sum_last_add2 = sum(str_to_int2)

checksum = sum_last_add1 + sum_last_add2

#Printing the type of digital card based on user input
if checksum % 10 == 0:
    if ccn[:2] == "34" or "37" and len(ccn) == 15:
        print("AMEX")
    elif ccn[:1] == "4" :
        if len(ccn) == 13 or 14 or 15 or 16:
            print("VISA")
    elif ccn[:2] == "51" or "52" or "53" or "54" or "55" :
        if len(ccn) == 16:
            print("MASTERCARD")
    else:
        print("INVALID")
else:
    print("INVALID")

Example 2: luhn algorithm python

$ pip install fast-luhn