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curriculum/challenges/english/blocks/learn-how-to-work-with-numbers-and-strings-by-implementing-the-luhn-algorithm/656880227dab4bd8fbc02d41.md

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--description--

Well done on completing this project.

As a final step, remove the print call from the verify_card_number function, and change the card_number back to something valid.

--hints--

You should not have a print call within the verify_card_number function.

js
({
    test: () => {
        const transformedCode = code.replace(/\r/g, "");
        const verify_card_number = __helpers.python.getDef("\n" + transformedCode, "verify_card_number");
        const { function_body } = verify_card_number;
        const no_comments = __helpers.python.removeComments(function_body);
        assert.notMatch(no_comments, /print\(/);
    }
})

You should change card_number back to something valid.

js
({
    test: () => {
        const spyCode = "a = ''\ndef printSpy(*x):\n    global a\n    a = str(x)\n" + code.replaceAll("print(", "printSpy(") + "\na";
        const out = runPython(spyCode);
        assert.notInclude(out, "INVALID!");
        assert.include(out, "VALID!");
    }
})

--seed--

--seed-contents--

py
--fcc-editable-region--
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
    print(total)
    return total % 10 == 0

def main():
    card_number = '4111-1111-4555-1141'
    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()
--fcc-editable-region--

--solutions--

py
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()