单例模式

单例模式：

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class MySocketClient:     __instance = None       # 单例模式（同一时间只有一个实例）     def __new__(cls, *args, **kwargs):         if MySocketClient.__instance is None:             MySocketClient.__instance = object.__new__(cls, *args, **kwd) #object.__new__ 实例化             ip_port = (configuration.get('server_ip'), configuration.get('server_port'))             cls.sk = socket.socket()             cls.conn = cls.sk.connect(ip_port)         return MySocketClient.__instance

　　如果MySocketClient.__instance为原始值，就对MySocketClient类进行实例化（object.__new__(cls, *args, **kwd)）并赋值给MySocketClient.__instance，

 

4.基于__new__方法实现的单例模式(推荐使用,方便)

1> 一个对象的实例化过程是先执行类的__new__方法,如果我们没有写,默认会调用object的__new__方法,返回一个实例化对象,然后再调用__init__方法,对这个对象进行初始化,我们可以根据这个实现单例.
2> 在一个类的__new__方法中先判断是不是存在实例,如果存在实例,就直接返回,如果不存在实例就创建.

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# encoding:utf-8 __author__ = 'Fioman' __time__ = '2020/5/26 12:36' import threading     class Singleton(object):     _instance_lock = threading.Lock()       def __init__(self, *args, **kwargs):         pass       def __new__(cls, *args, **kwargs):         if not hasattr(cls, '_instance'):             with Singleton._instance_lock:                 if not hasattr(cls, '_instance'):                     Singleton._instance = super().__new__(cls)               return Singleton._instance     obj1 = Singleton() obj2 = Singleton() print(obj1, obj2)     def task(arg):     obj = Singleton()     print(obj)     for i in range(10):     t = threading.Thread(target=task, args=[i, ])     t.start()