code: def book_number(self, name):
          '''Return number of book with given name.'''
          try:
              number = self.cur.execute("SELECT number FROM book WHERE name= ?;", [name]).fetchone()
          except:
              self.error("cannot look up number of book with name %s" % name)
          return(numberf book_number(self, name):
          '''Return number of book with given name.'''
          try:
              number = self.cur.execute("SELECT number FROM book WHERE name= ?;", [name]).fetchone()
          except:
              self.error("cannot look up number of book with name %s" % name)
          return(number)
docs: Return number of book with given name.