Debug an ISBN Validator - Debug an ISBN Validator

Python
1

Tell us what’s happening:

I don’t understand why i’m failing tests 9, 19, and 20. (1530051126, 10), (080442957X, 10), and (9781947172104, 13) should be valid but the program says there not. i dont understand why and how to fix it i’ve tried everything i know so far.

Your code so far

def validate_isbn(isbn, length):
    if len(isbn) != length:
        print(f'ISBN-{length} code should be {length} digits long.')
        return
    main_digits = isbn[0:length]
    print(main_digits)
    given_check_digit = isbn[length-1]
    main_digits_list = [int(digit) for digit in main_digits]
    # Calculate the check digit from other digits
    if length == 10:
        expected_check_digit = calculate_check_digit_10(main_digits_list)
        print(f'Expected Check Digit: {expected_check_digit}')
    else:
        expected_check_digit = calculate_check_digit_13(main_digits_list)
    # Check if the given check digit matches with the calculated check digit
    if(given_check_digit == 10):
        given_check_digit = 'X'
    elif(given_check_digit == 11):
        given_check_digit = '0'
    print(f'Given Check Digit: {given_check_digit}')
    if given_check_digit == expected_check_digit:
        print('Valid ISBN Code.')
    else:
        print('Invalid ISBN Code.')
def calculate_check_digit_10(main_digits_list):
    # Note: You don't have to fully understand the logic in this function.
    digits_sum = 0
    # Multiply each of the first 9 digits by its corresponding weight (10 to 2) and sum up the results
    for index, digit in enumerate(main_digits_list):
        digits_sum += digit * (10 - index)
    # Find the remainder of dividing the sum by 11, then subtract it from 11
    result = 11 - digits_sum % 11
    # The calculation result can range from 1 to 11.
    # If the result is 11, use 0.
    # If the result is 10, use upper case X.
    # Use the value as it is for other numbers.
    if result == 11:
        expected_check_digit = '0'
    elif result == 10:
        expected_check_digit = 'X'
    else:
        expected_check_digit = str(result)
    return expected_check_digit
def calculate_check_digit_13(main_digits_list):
    # Note: You don't have to fully understand the logic in this function.
    digits_sum = 0
    # Multiply each of the first 12 digits by 1 and 3 alternately (starting with 1), and sum up the results
    for index, digit in enumerate(main_digits_list):
        if index % 2 == 0:
            digits_sum += digit * 1
        else:
            digits_sum += digit * 3
    # Find the remainder of dividing the sum by 10, then subtract it from 10
    result = 10 - digits_sum % 10
    # The calculation result can range from 1 to 10.
    # If the result is 10, use 0.
    # Use the value as it is for other numbers.
    if result == 10:
        expected_check_digit = '0'
    else:
        expected_check_digit = str(result)
    return expected_check_digit
def main():
    user_input = input('Enter ISBN and length: ')
    if ',' not in user_input:
        print('Enter comma-separated values.')
        return
    values = user_input.split(',')
    isbn = values[0]
    try:
        length = int(values[1])
    except ValueError:
        print('Length must be a number.')
    
    try:
        isbnTemp = int(isbn)
    except ValueError:
        print('Invalid character was found.')
    if length == 10 or length == 13:
        validate_isbn(isbn, length)
    else:
        print('Length should be 10 or 13.')

#main()

validate_isbn('1530051126', 10)

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Challenge Information:

Debug an ISBN Validator - Debug an ISBN Validator

2

Should main_digits and main_digits_list include the check digit?

3

Oh wow. I cracked my head for so long trying to figure out where I was going wrong with the code. Even included validating the ISBN codes individually in Excel after understanding the code for the check digit functions.

Never once struck me that the check digit shouldn’t be included in the math! Thanks so much :folded_hands: