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Diffstat (limited to 'netmodel/util/singleton.py')
-rw-r--r-- | netmodel/util/singleton.py | 41 |
1 files changed, 41 insertions, 0 deletions
diff --git a/netmodel/util/singleton.py b/netmodel/util/singleton.py new file mode 100644 index 00000000..4aaff9ee --- /dev/null +++ b/netmodel/util/singleton.py @@ -0,0 +1,41 @@ +#!/usr/bin/env python3 +# -*- coding: utf-8 -*- +# +# Copyright (c) 2017 Cisco and/or its affiliates. +# +# Licensed 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(type): + """ + Classes that inherit from Singleton can be instanciated only once + + See also + http://stackoverflow.com/questions/6760685/creating-a-singleton-in-python + """ + + def __init__(cls, name, bases, dic): + super(Singleton,cls).__init__(name,bases,dic) + cls.instance=None + + def __call__(cls, *args, **kw): + if cls.instance is None: + cls.instance=super(Singleton,cls).__call__(*args,**kw) + return cls.instance + + def _drop(cls): + "Drop the instance (for testing purposes)." + if cls.instance is not None: + del cls.instance + cls.instance = None + |