code: def update(self, table, rowupdate, where):
          
          (sql, values) = sqlupdate(table, rowupdate, where)
          return self.execute(sql, values)
docs: Update matching records.
          - rowupdate is a dict with updated fields, e.g. {'name': 'John'}.
          - See `sqlwhere` for where clause.
  
          Returns the number of rows updated.
  
          >>> import getpass
          >>> s = DB(dbname='test', user=getpass.getuser(), host='localhost',
          ... password='')
          >>> s.execute('drop table if exists t2')
          >>> s.execute('create table t2 (id int, name text)')
          >>> s.insert('t2', {'id': 1, 'name': 'Toto'})
          >>> s.select('t2')
          [{'id': 1, 'name': 'Toto'}]
          >>> s.update('t2', {'name': 'Tata'}, {'id': 1})
          1
          >>> s.select('t2')
          [{'id': 1, 'name': 'Tata'}]