def update(self, table, rowupdate, where):
(sql, values) = sqlupdate(table, rowupdate, where)<EOL>return self.execute(sql, values)<EOL>
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'}]