python中的对象赋值(等号赋值、深复制、浅复制)

来源：互联网发布：ubuntu搭建hadoop集群编辑：程序博客网时间：2024/06/06 01:00

代码：

import copyclass Obj():    def __init__(self,arg):        self.x=argif __name__ == '__main__':    obj1=Obj(1)    obj2=Obj(2)    obj3=Obj(3)    obj4=Obj(4)    lst=[obj1,obj2,obj3,obj4]    lst1=lst    lst2=copy.copy(lst)    lst3=copy.deepcopy(lst)    print(id(lst),id(lst1),id(lst2),id(lst3))

输出：

(37271888, 37271888, 37688456, 37271816)

从以上输出可以发现，通过等号直接赋值，只能使lst1获得lst的引用，lst1与lst共享同一份数据。而lst2和lst3都获得了自己的一份数据(list)，lst2和lst3的区别见下面的代码：

print id(lst),'------>',    for obj in lst:        print id(obj),    print ''    print id(lst2),'------>',    for obj in lst2:        print id(obj),    print ''    print id(lst3),'------>',    for obj in lst3:        print id(obj),

输出：

13887824 ------> 13888184 13939704 13938768 13941864 13960256 ------> 13888184 13939704 13938768 13941864 13887752 ------> 13960184 13960544 13960616 13960688

从以上输出可以发现，lst、lst2、lst3对应的list各不相同，但lst和lst2包含的对象是相同的，也就是说，浅复制没有进行递归复制，仅复制了最外一层

官网对二者区别的描述：

The difference between shallow and deep copying is only relevant for compound objects (objects that contain other objects, like lists or class instances):

A shallow copy constructs a new compound object and then (to the extent possible) inserts references into it to the objects found in the original.
A deep copy constructs a new compound object and then, recursively, inserts copies into it of the objects found in the original.

0 0