python3 类的单例模式

# coding:utf-8
class Singleton():
    __instance = None

    def __init__(self):
        print("我是init方法.")

    def __new__(cls):
        if not Singleton.__instance:
            Singleton.__instance = object.__new__(cls)
        return Singleton.__instance

obj1 = Singleton()
obj2 = Singleton()
print(id(obj1), id(obj2))

执行结果:
我是init方法.
我是init方法.
12270064 12270064