Tell us what’s happening:
I’m struggling with task 9 and 20. They’re supposed to be valid ISBNs but the check digits aren’t adding up properly. I’ve checked the maths but it seems right to me…? Any help is appreciated
Your code so far
def validate_isbn(isbn, length):
if len(isbn) != length:
print(f'ISBN-{length} code should be {length} digits long.')
return
if length == 10:
if isbn.lower()[-1]=="x":
main_digits = isbn[0:length-1]
else:
main_digits = isbn[0:length]
else:
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)
else:
expected_check_digit = calculate_check_digit_13(main_digits_list)
# Check if the given check digit matches with the calculated check digit
print(f'Comparing {given_check_digit} and {expected_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
print(digits_sum)
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
print(main_digits_list)
for index, digit in enumerate(main_digits_list):
if index % 2 == 0:
print(index)
digits_sum += digit * 1
else:
print(index)
digits_sum += digit * 3
# Find the remainder of dividing the sum by 10, then subtract it from 10
print(digits_sum)
result = 10 - digits_sum % 10
print(result)
# 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: ')
try:
values = user_input.split(',')
isbn = values[0]
print(f"{isbn} with {len(isbn)}")
length = int(values[1])
print(length)
if length == 13:
if not isinstance(isbn,int):
print("Invalid character was found.")
elif length == 10:
if isbn.lower()[-1]=="x":
if not isinstance(int(isbn[:len(isbn)-1]),int):
print("Invalid character was found.")
else:
if not isinstance(isbn,int):
print("Invalid character was found.")
if length == 10 or length == 13:
validate_isbn(isbn, length)
else:
print('Length should be 10 or 13.')
except IndexError:
print("Enter comma-separated values.")
except ValueError:
print("Length must be a number.")
validate_isbn("9781947172104", 13)
# main()
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Challenge Information:
Debug an ISBN Validator - Debug an ISBN Validator
