Funkce programu · Luhnova kontrola číslic ASCII

def luhn_valid(text):
    if type(text) is not str or not 2 <= len(text) <= 64:
        raise ValueError("luhn.length")
    if any(char < "0" or char > "9" for char in text):
        raise ValueError("luhn.alphabet")
    total = 0
    for index, char in enumerate(reversed(text)):
        digit = ord(char) - ord("0")
        if index % 2:
            digit *= 2
            if digit > 9:
                digit -= 9
        total += digit
    return total % 10 == 0