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  • 单例模式

    单例模式

    1 使用__new__方法

    class Singleton(object):
        def __new__(cls, *args, **kw):
            if not hasattr(cls, '_instance'):
                orig = super(Singleton, cls)
                cls._instance = orig.__new__(cls, *args, **kw)
            return cls._instance
    
    class MyClass(Singleton):
        a = 1

    2 共享属性

    创建实例时把所有实例的__dict__指向同一个字典,这样它们具有相同的属性和方法.

    class Borg(object):
        _state = {}
        def __new__(cls, *args, **kw):
            ob = super(Borg, cls).__new__(cls, *args, **kw)
            ob.__dict__ = cls._state
            return ob
    
    class MyClass2(Borg):
        a = 1

    3 装饰器版本

    def singleton(cls, *args, **kw):
        instances = {}
        def getinstance():
            if cls not in instances:
                instances[cls] = cls(*args, **kw)
            return instances[cls]
        return getinstance
    
    @singleton
    class MyClass:
      ...

    4 import方法

    作为python的模块是天然的单例模式

    # mysingleton.py
    class My_Singleton(object):
        def foo(self):
            pass
    
    my_singleton = My_Singleton()
    
    # to use
    from mysingleton import my_singleton
    
    my_singleton.foo()
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  • 原文地址:https://www.cnblogs.com/yangxiaolan/p/6021241.html
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