luhn algorithm python

#Worse
#This is the longer 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)

ccn_string = str(ccn)

length_var = len(ccn)

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

# Condition for digital card number with even length
elif length_var % 2 == 0:
    even_num1 = ccn
    even_num2 = " " + ccn

    even_num3 = "".join(even_num1[::2])
    even_num4 = "".join(even_num2[::2])

    even_alternate1 = even_num3.replace(" ", "")
    even_alternate2 = even_num4.replace(" ", "")

    even_sep1 = split_char(even_alternate1)
    even_sep2 = split_char(even_alternate2)

    even_str_to_int1 = list_str_to_int(even_sep1)
    even_str_to_int2 = list_str_to_int(even_sep2)

    even_str_2_1 = list_multiplied_by_2(even_str_to_int1)

    even_int_to_str1 = list_int_to_str(even_str_2_1)
    even_sep_digits1 = ""
    for i in even_int_to_str1:
        even_sep_digits1 += "".join(i)

    even_sep3 = split_char(even_sep_digits1)

    even_str_to_int3 = list_str_to_int(even_sep3)
    even_sum_last_add1 = sum(even_str_to_int3)

    even_sum_last_add2 = sum(even_str_to_int2)

    even_checksum = even_sum_last_add1 + even_sum_last_add2

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

# Condition for digital card number with odd length
elif length_var % 2 == 1:
    odd_num1 = " " + ccn
    odd_num2 = ccn

    odd_num3 = "".join(odd_num1[::2])
    odd_num4 = "".join(odd_num2[::2])

    odd_alternate1 = odd_num3.replace(" ", "")
    odd_alternate2 = odd_num4.replace(" ", "")

    odd_sep1 = split_char(odd_alternate1)
    odd_sep2 = split_char(odd_alternate2)

    odd_str_to_int1 = list_str_to_int(odd_sep1)
    odd_str_to_int2 = list_str_to_int(odd_sep2)

    odd_str_2_1 = list_multiplied_by_2(odd_str_to_int1)

    odd_int_to_str1 = list_int_to_str(odd_str_2_1)
    odd_sep_digits1 = ""
    for i in odd_int_to_str1:
        odd_sep_digits1 += "".join(i)

    odd_sep3 = split_char(odd_sep_digits1)

    odd_str_to_int3 = list_str_to_int(odd_sep3)
    odd_sum_last_add1 = sum(odd_str_to_int3)

    odd_sum_last_add2 = sum(odd_str_to_int2)

    odd_checksum = odd_sum_last_add1 + odd_sum_last_add2

    #Printing the type of digital card based on user input
    if odd_checksum % 10 == 0:
        if ccn_string[:2] == "34" or "37" and len(ccn_string) == 15:
            print("AMEX")
        elif len(ccn_string) == 13 or 15 and ccn_string[:1] == "4":
            print("VISA")
        else:
            print("INVALID")
    else:
        print("INVALID")