Tell us what’s happening:
I afraid I don’t understand the initial inputs.
main_digits_list = [int(digit) for digit in main_digits]
I see others edit this line making it main_degits[-1]. I think this is removing the check digit from the calculation which results in a valid ISBN. The problem is that it also makes the second ISBN valid that is supposed to return as invalid. Since the only difference is the last digit: 1530051126(valid) vs 1530051125(invalid).
Without adding the -1 the check doesn’t ever return valid.
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(f"main digits = {main_digits}")
given_check_digit = isbn[length-1]
print(f"given check digit = {given_check_digit}")
main_digits_list = [int(digit) for digit in main_digits]
#print(f"main digits list = {main_digits_list}")
# Calculate the check digit from other digits
if length == 10:
expected_check_digit = calculate_check_digit_10(main_digits_list)
print(f"validate isbn: 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 == expected_check_digit:
print('Valid ISBN Code.')
else:
print('Invalid ISBN Code.')
print(f"check digit = {given_check_digit}, expected check digit returned: {expected_check_digit}")
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)
print(f"sum of digits = {digits_sum}")
# Find the remainder of dividing the sum by 11, then subtract it from 11
result = 11 - digits_sum % 11
print(f"result of 11 - {digits_sum % 11} = {result}")
# 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'
print(f"calc check digit: expected check digit = {expected_check_digit}")
elif result == 10:
expected_check_digit = 'X'
#print(expected_check_digit)
else:
expected_check_digit = str(result)
#print(expected_check_digit)
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(',')
#print(values)
isbn = values[0]
#print(isbn)
length = int(values[1])
#print(length)
if length == 10 or length == 13:
validate_isbn(isbn, length)
else:
print('Length should be 10 or 13.')
main()
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Challenge Information:
Debug an ISBN Validator - Debug an ISBN Validator