Python单例模式

1 使用__new__方法
1 class Singleton(object):
2     def __new__(cls, *args, **kw):
3          if not hasattr(cls, '_instance'):
4              orig = super(Singleton, cls) 
5              cls._instance = orig.__new__(cls, *args, **kw)                         
6          return cls._instance
7 
8 class MyClass(Singleton):
9     a = 1

 

2 共享属性
创建实例时把所有实例的__dict__指向同一个字典,这样它们具有相同的属性和方法.
1 class Borg(object):
2     _state = {} 
3     def __new__(cls, *args, **kw):
4     ob = super(Borg, cls).__new__(cls, *args, **kw)
5     ob.__dict__ = cls._state
6     return ob
7 
8 class MyClass2(Borg):
9     a = 1

 

3 装饰器版本
 1 def singleton(cls, *args, **kw):
 2     instances = {}
 3     def getinstance():
 4         if cls not in instances:
 5             instances[cls] = cls(*args, **kw)
 6          return instances[cls] 
 7     return getinstance
 8 
 9 @singleton
10 class MyClass:
11  ...

 

posted @ 2020-04-22 10:05  燕十三丶  阅读(161)  评论(0)  编辑  收藏  举报
AmazingCounters.com