Jun 27, 2021

Python-单例模式

单例模式

包导入模式

class Singleton:
    pass

singleton = Singleton()

装饰器模式

def SingletonDec(cls):
    _instance = {}

    def _singleton(*args, **kwargs):
        if cls not in _instance:
            _instance[cls] = cls(*args, **kwargs)
        return _instance[cls]

    return _singleton

@SingletonDec
class Foo:
    pass

类

class Singleton:
    def __new__(cls, *args, **kwargs):
        if not hasattr(cls, '_instance'):
            cls._instance = super().__new__(cls)
        return cls._instance

元类

class Singleton(type):
    def __call__(cls, *args, **kwargs):
        if not hasattr(cls, '_instance'):
            cls._instance = super().__call__(*args, **kwargs)
        return cls._instance

class Foo(metaclass=Singleton):
    pass