Python 笔记之单例

Katherine10292024-11-19 16:34

复制代码

#单例模式：只产生一次地址
#开发模式：单例模式

class singleleton:
    #私有化当前实例(对于内存的优化，保持地址)
    #单例的地址就存在于__instance中
    __instance=None
    name='jack'
    #重写__new__
    def __new__(cls):
        print('__new__')
        if cls.__instance is None:
            print('是空')
            cls.__instance=object.__new__(cls)
            print(cls.__instance)
            return cls.__instance
        else:
            print('不是空')
            return cls.__instance
    def show(self,n):
        print('--->show {0} is {1}'.format(self.name,n))
print(dir(singleleton))#查看类中所有的attribute
s=singleleton()
s1=singleleton()
print(s)
print(s1)
s.show(5)
s1.show(7)

输出：

['class', 'delattr', 'dict', 'dir', 'doc', 'eq', 'format', 'ge', 'getattribute', 'gt', 'hash', 'init', 'init_subclass', 'le', 'lt', 'module', 'ne', 'new', 'reduce', 'reduce_ex', 'repr', 'setattr', 'sizeof', 'str', 'subclasshook', 'weakref', '_singleleton__instance', 'name', 'show']

new

是空

<main.singleleton object at 0x000001D38C2F7130>

new

不是空

<main.singleleton object at 0x000001D38C2F7130>

--->show jack is 5

--->show jack is 7