Source code for taurus.core.util.singleton

#!/usr/bin/env python

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# This file is part of Taurus
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# http://taurus-scada.org
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# Copyright 2011 CELLS / ALBA Synchrotron, Bellaterra, Spain
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# Taurus is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
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# Taurus is distributed in the hope that it will be useful,
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# GNU Lesser General Public License for more details.
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"""This module contains a class which can be used as a super class for all
classes that need to implement the Singleton design pattern."""

from builtins import object

__all__ = ["Singleton"]

__docformat__ = "restructuredtext"


[docs]class Singleton(object): """ This class allows Singleton objects The __new__ method is overriden to force Singleton behaviour. The Singleton is created for the lowest subclass. Usage:: from taurus.core.util.singleton import Singleton class MyManager(Singleton): def init(self, *args, **kwargs): print "Singleton initialization" command line:: >>> manager1 = MyManager() Singleton initialization >>> manager2 = MyManager() >>> print(manager1,manager2) <__main__.MyManager object at 0x9c2a0ec> <__main__.MyManager object at 0x9c2a0ec> Notice that the two instances of manager point to the same object even though you *tried* to construct two instances of MyManager. .. warning:: although __new__ is overriden __init__ is still being called for each instance=Singleton() """ # Singleton object _the_instance = None def __new__(cls, *p, **k): # srubio: added type checking if cls != type(cls._the_instance): cls._the_instance = object.__new__(cls) # srubio: added init_single check if 'init_single' in cls.__dict__: cls._the_instance.init_single(*p, **k) else: cls._the_instance.init(*p, **k) return cls._the_instance
[docs] def init(self, *p, **k): pass