#单例模式#装饰器版本def singleton(cls):    instances = {}    def getinstance():        if cls not in instances:            instances[cls] = cls()        return instances[cls]    return getinstance@singletonclass Myclass:    passins1 = Myclass()ins2 = Myclass()print(id(ins1),id(ins2))#43877264 43877264#import方法  --> 天然的单例模式#mysingleton.py  一个py文件class My_Singleton(object):    def foo(self):        passmy_singleton = My_Singleton()#to use from mysingleton# import my_singleton  在另外一个文件中导入类的实例对象my_singleton.foo()#使用__new__方法class Singleton(object):    def __new__(cls):        if not hasattr(cls,'_instance'):            orig = super(Singleton,cls)            cls._instance = orig.__new__(cls)        return cls._instance# class MyClass(singleton):#     a = 1ins3 = Singleton()ins4 = Singleton()print(id(ins3),id(ins4))#43877656 43877656