def close(self):
		'''关闭与数据库的连接'''
		if VERBOSE:
			print 'Database connection CLOSE.'
		self.conn.close()
def check_prereq(self, prereqMode = 0):
        self._exit_modes_beyond(prereqMode)
        if len(self.modeList) <= prereqMode:
            raise Exception("Attempted to enter menu when prerequist mode was not entered, expected: %d" % prereqMode)