python----单例

class foo():
    __v = None

    @classmethod
    def get_instance(cls):
        if cls.__v:
            return cls.__v
        else:
            cls.__v = foo()
            return cls.__v

obj1 = foo.get_instance()
obj2 = foo.get_instance()

print(obj1)
print(obj2)

########################
‘‘‘
运行结果为：

<__main__.foo object at 0x00000198CD392F98>
<__main__.foo object at 0x00000198CD392F98>
‘‘‘