297-Credit card number validity checker

"""Code snippets vol-60
   297-Credit card number validity checker

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Requirements:
None

origin:
#https://github.com/Shankhesh-16/Credit-Card-Checker/blob/master/Credit%20Card%20Checker.py
"""
# Insert card number below
credit_card_number = [5, 4, 9, 6, 2, 7, 4, 1, 4, 3, 1, 4, 1, 5, 2, 2]


def cc_checker_function(credit_card_number):
    if len(credit_card_number) == 16:

        after_doubling_number = []
        for index in range(len(credit_card_number)):
            if index % 2 == 0:
                after_doubling_number.append(credit_card_number[index] * 2)
            else:
                after_doubling_number.append(credit_card_number[index])

        # print(after_doubling_number)

        after_subtracting_list = []
        for index1 in range(len(after_doubling_number)):
            if index1 % 2 == 0 and after_doubling_number[index1] > 9:
                nine_subtraction_value = after_doubling_number[index1] - 9
                after_subtracting_list.append(nine_subtraction_value)
            else:
                after_subtracting_list.append(after_doubling_number[index1])

        # print(after_subtracting_list)

        list_to_number = ""
        for index2 in range(len(credit_card_number)):
            list_to_number += str(credit_card_number[index2])

        sum_of_final_list = sum(after_subtracting_list)

        if sum_of_final_list % 10 == 0:
            print("VALID!!")
            print(list_to_number)
        else:
            print("INVALID")
            print(list_to_number)

    else:
        print('Please check the length of the number.')


cc_checker_function(credit_card_number)