obj.connect() => True or raise Error from MySQLdb.
        You aren't suggested to use this function by your hand,
        because this func may cause Exception.

def connect(self):
        """obj.connect() => True or raise Error from MySQLdb.
        You aren't suggested to use this function by your hand,
        because this func may cause Exception.
        """
        self.conn = self.db_module.connect(
                host=self.host, port=int(self.port), user=self.user,
                passwd=self.passwd, db=self.dbname, charset=self.charset,
                cursorclass=self.cursorclass)
        self.conn.autocommit(self.autocommit)
        return True