单例模式

一、基于__new__

class Single:     _instance = None      def __new__(cls, *args, **kwargs):         if not cls._instance:             cls._instance = super(Single, cls).__new__(cls, *args, **kwargs)         return cls._instance   class Demon(Single):      def foo(self):         print("Hi")   d1 = Demon() d2 = Demon() print(id(d1))　　# 2110545800776 print(id(d2))　　# 2110545800776

二、基于模块

1、重点：一个文件在一个项目中只加载一次

来源: https://www.cnblogs.com/wt7018/p/11366942.html