Singleton in Python
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import functools def singleton(cls): """ Use class as singleton. """ cls.__new_original__ = cls.__new__ @functools.wraps(cls.__new__) def singleton_new(cls, *args, **kw): it = cls.__dict__.get('__it__') if it: return it cls.__it__ = it = cls.__new_original__(cls, *args, **kw) it.__init_original__(*args, **kw) return it cls.__new__ = singleton_new cls.__init_original__ = cls.__init__ cls.__init__ = object.__init__ return cls |
Sample use
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@singleton class Foo: def __new__(cls): cls.x = 10 return object.__new__(cls) def __init__(self): assert self.x == 10 self.x = 15 assert Foo().x == 15 Foo().x = 20 assert Foo().x == 20 |
