credit_card.py

"""Computes if a credit card number is valid.

Daniel Franklin <[email protected]>
HW due 15 Nov 2019
"""

def normalize_input(input_str):
    """Normalize an input string into an easier to process format.

    :param input_str: A string of user input in form "xxxx-xxxx-xxxx-xxxx"
    :return list[int]: The cc number as a list of digits
    """
    return [int(n) for n in input_str.replace("-", "")]


def validate_card(num):
    """Validate if a number is a valid credit card number.

    :param num: The number to check as a list[int]
    :return bool: If the number is valid
    """
    requirements = [
        num[0] == 4,
        num[4 - 1] == num[5 - 1] + 1,
        num[1 - 1] * num[5 - 1] * num[9 - 1] == 24,
        sum(num) % 4 == 0,
        sum(num[:4]) == sum(num[-4:]) - 1,
        (num[1 - 1] * 10 + num[2 - 1]) + (num[7 - 1] * 10 + num[8 - 1]) == 100
    ]

    return not (False in requirements)


def main(card_to_test):
    return validate_card(normalize_input(card_to_test))


def test():
    """Check the program against test cases.

    Throws AssertionError if a test case fails.
    """
    tests = [
        ["4132-1459-6972-3341", True],
        ["4442-1056-6063-4434", True],
        ["4104-3059-2802-1234", True],
        ["4444-3333-2222-2111", False],
        ["5105-1051-0510-5100", False]
    ]

    for (input_str, expected_out) in tests:
        print(f"Testing that \"{input_str}\" is a valid card number")
        assert(main(input_str) == expected_out)


if __name__ == '__main__':
    card_to_test = input("Card to test: ")

    if main(card_to_test):
        result_as_str = ""
    else:
        result_as_str = "NOT "

    print(f"The credit card number {card_to_test} is {result_as_str}valid")

credit_card_test_case_creator.py

from random import randint
from credit_card import validate_card # my checking function


NUMBER_OF_CARDS_TO_FIND = 2


def pretty_format_card(nums):
	"""Format a list of card digits into a the form xxxx-xxxx-xxxx-xxxx."""
	return "-".join(
		"".join([str(num) for num in group])
		for group in [nums[:4], nums[4:8], nums[8:12], nums[12:]])


iterations = 0
found_cards = []
while True:
	# every 1,000,000th time this loop runs, print how many times it has run
	if iterations % 10**6 == 0:
		print(iterations)

	# create a list of the number 4 followed by 15 random numbers
	nums = [4]
	while(len(nums) < 16):
		nums.append(randint(0, 9))

	if validate_card(nums):
		found_card = pretty_format_card(nums)

		print(f"Found result: {found_card}")
		found_cards.append(found_card)

		if len(found_cards) >= NUMBER_OF_CARDS_TO_FIND:
			break

	iterations += 1


print("\n\n")
for card in found_cards:
	print(card)