| # |
| # Licensed to the Apache Software Foundation (ASF) under one or more |
| # contributor license agreements. See the NOTICE file distributed with |
| # this work for additional information regarding copyright ownership. |
| # The ASF licenses this file to You under the Apache License, Version 2.0 |
| # (the "License"); you may not use this file except in compliance with |
| # the License. You may obtain a copy of the License at |
| # |
| # http://www.apache.org/licenses/LICENSE-2.0 |
| # |
| # Unless required by applicable law or agreed to in writing, software |
| # distributed under the License is distributed on an "AS IS" BASIS, |
| # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| # See the License for the specific language governing permissions and |
| # limitations under the License. |
| # |
| |
| |
| class Singleton(object): |
| """ |
| This is to ensure a single process can only have one instance of agent. |
| Written by Guido van Rossum to implement a singleton pattern. |
| https://www.python.org/download/releases/2.2/descrintro/#__new__ |
| Classes that inherit from this class will be singletons. |
| """ |
| def __new__(cls, *args, **kwds): |
| it = cls.__dict__.get('__it__') |
| if it is not None: |
| return it |
| cls.__it__ = it = object.__new__(cls) |
| it.init(*args, **kwds) |
| return it |
| |
| def init(self, *args, **kwds): |
| pass |
