# If the sum is divisible by 10, the number is valid return sum(card_number) % 10 == 0
# Double every second digit for i in range(1, len(card_number), 2): card_number[i] = card_number[i] * 2 # Subtract 9 from numbers over 9 if card_number[i] > 9: card_number[i] -= 9 cc checker.rar
# Reverse the card number card_number = card_number[::-1] # If the sum is divisible by 10,