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curriculum/challenges/english/blocks/learn-how-to-work-with-numbers-and-strings-by-implementing-the-luhn-algorithm/656b47dc2cf39e37025dc033.md

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--description--

Reverse the order of the digits in the last four digits of card_number, by using a slice with a step of -1. You can use either negative or positive indices for the start and end indices.

--hints--

You should have card_number_reversed = card_number[-1:-5:-1] within the verify_card_number function. Expected --fcc-actual-- to equal --fcc-expected--.

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

        const pyCode = `
card_number = "4111111145551142"
${def}
${function_body.match(/ +/)[0]}return card_number_reversed

verify_card_number(card_number)
`;
        const out = runPython(pyCode, {});
        assert.equal(out, "2411");
    }
})

--seed--

--seed-contents--

py
--fcc-editable-region--
def verify_card_number(card_number):
    sum_of_odd_digits = 0
    card_number_reversed = card_number[0:4:2]
    print(card_number_reversed)
    
--fcc-editable-region--
def main():
    card_number = '4111-1111-4555-1142'
    card_translation = str.maketrans({'-': '', ' ': ''})
    translated_card_number = card_number.translate(card_translation)

    print(translated_card_number)

    verify_card_number(translated_card_number)

main()