python中的单例

 1 class Single:
 2     instance = None
 3 
 4     def __new__(cls, *args, **kwargs):
 5         if cls.instance:
 6             return cls.instance
 7         cls.instance = object.__new__(cls)
 8         return cls.instance
 9 
10 o1 = Single()
11 o2 = Single()
12 print(o1)  # <__main__.Single object at 0x00000000021EDAC8>
13 print(o2)  # <__main__.Single object at 0x00000000021EDAC8>