Python中的几种设计模式

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  1. 单例模式：
    法一：通过类的new()方法，但是个人感觉没有装饰器方便
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class Singleton(object):
    __instance = None
    
    def __init__(self):
        pass

    def __new__(cls, *args, **kwd):
        if Singleton.__instance is None:
            Singleton.__instance = object.__new__(cls, *args, **kwd)
        return Singleton.__instance

class MyClass(Singleton):
    aa = 88

instance1 = MyClass()
instance2 = MyClass()
print id(instance1)
print id(instance2)
139984856635600
139984856635600
  1. 用装饰器来实现
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    def singleton(cls, *args, **kw):
        instances = {}
        def _singleton():
            if cls not in instances:
                instances[cls] = cls(*args, **kw)
            return instances[cls]
        return _singleton

    @singleton
    class MyClass1(object):
        aa = 56
    instance1 = MyClass1()
    instance2 = MyClass1()
    print id(instance1)
    #139764123790288
    print id(instance2)
    #139764123790288