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一个对象只允许被一次创建,一个类只能创建一个对象,并且提供一个全局访问点。
特点:全局唯一,允许更改
优点:
缺点:
class MetaClass(tyPE): def __call__(self, *args, **kwargs): """ self : class Singleton """ if not hasattr(self, "ins"): insObject = super(__class__, self).__call__(*args, **kwargs) setattr(self, "ins", insObject) return getattr(self, "ins") class Singleton(object, metaclass=MetaClass): pass if __name__ == "__main__": ins = Singleton() PRint(id(ins)) ins = Singleton() print(id(ins))
class ParentClass: def __new__(cls, *args, **kwargs) -> object: """ cls : class Singeton """ if not hasattr(cls, "ins"): insObject = super(__class__, cls).__new__(cls, *args, **kwargs) setattr(cls, "ins", insObject) return getattr(cls, "ins") class Singleton(ParentClass): pass if __name__ == "__main__": ins = Singleton() print(id(ins)) ins = Singleton() print(id(ins))
def warpper(clsObject): def inner(*args, **kwargs): if not hasattr(clsObject, "ins"): insObject = clsObject(*args, **kwargs) setattr(clsObject, "ins", insObject) return getattr(clsObject, "ins") return inner @warpper class Singleton: pass if __name__ == "__main__": ins = Singleton() print(id(ins)) ins = Singleton() print(id(ins))
- foo.py --> ins = Singleton() - bar.py --> From foo import ins
class Singleton: @classmethod def getSingletonInstanceObject(cls, *args, **kwargs): if not hasattr(cls, "ins"): insObject = cls(*args, **kwargs) setattr(cls, "ins", insObject) return getattr(cls, "ins") if __name__ == "__main__": ins = Singleton.getSingletonInstanceObject() print(id(ins)) ins = Singleton.getSingletonInstanceObject() print(id(ins))
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