Task

Validate the check digit of an ISBN-13 code:

   Multiply every other digit by  3.
   Add these numbers and the other digits.
   Take the remainder of this number after division by  10.
   If it is  0,   the ISBN-13 check digit is correct.


Use the following codes for testing:

   978-1734314502       (good)
   978-1734314509         (bad)
   978-1788399081       (good)
   978-1788399083         (bad)


Show output here, on this page



See also

   for details:   13-digit ISBN method of validation.       (installs cookies.)


def is_isbn13(n):
    n = n.replace('-','').replace(' ', '')
    if len(n) != 13:
        return False
    product = (sum(int(ch) for ch in n[::2]) 
               + sum(int(ch) * 3 for ch in n[1::2]))
    return product % 10 == 0
 
if __name__ == '__main__':
    tests = '''
978-1734314502
978-1734314509
978-1788399081
978-1788399083'''.strip().split()
    for t in tests:
        print(f"ISBN13 {t} validates {is_isbn13(t)}")