Debug an ISBN Validator - Debug an ISBN Validator

Python
1

Tell us what’s happening:

Please can someone tell me what is wrong with my code for 11, 12 and 13 to still give errors, I have done everything possible to solve this.

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[:-1]
    given_check_digit = isbn[-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)
    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 == 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: ')
    values = user_input.split(',')
    if "," not in user_input:
        print('Enter comma-separated values.')
        
    try:
        isbn = int(values[0])
    except ValueError:
        print('Invalid character was found.')

    try:
        length = int(values[1])
    except ValueError:
        print('Length must be a number.')

    if length == 10 or length == 13:
        print('Valid ISBN Code.')
        validate_isbn(isbn, length)
    elif length != 13:
        print('Length should be 10 or 13.')
    
# main()

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Challenge Information:

Debug an ISBN Validator - Debug an ISBN Validator

2

Test your code. I’m seeing an error in the console when I test #12:

Enter ISBN and length: 
9781530051120,10
Valid ISBN Code.
Traceback (most recent call last):
  File "main.py", line 83, in <module>
  File "main.py", line 79, in main
  File "main.py", line 2, in validate_isbn
TypeError: object of type 'int' has no len()
3

That is what I have been trying to do. 11, 12 and 13 are so problematic. I do not know why it is so picky on what it wants.

4

I figured it out. I need to do if len(str(isbn)) != length: and then introduced the if not isbn.isdigit(): since isbn is a string when received from the user input