6.Python depth Copy

Python depth copy

The process of assigning a variable value:

# -*-coding:utf-8 -*-__author__ = ‘xiaojiaxin‘__file_name__ = ‘shallowcopy_deepcopy‘#当拷贝数据足够多的时候，浪费空间# str1=[1,"jiaxin","john"]# str2=[1,"jiaxin","john"]# print(str1)# print(str2)

Copy method

str1=[1,"jiaxin","john"]str2=str1.copy()print(str1)print(str2)# [1, ‘jiaxin‘, ‘john‘]# [1, ‘jiaxin‘, ‘john‘]str2[0]=10;print(str1)print(str2)# [1, ‘jiaxin‘, ‘john‘]# [10, ‘jiaxin‘, ‘john‘]str3=[[1,2],"jiaxin",‘john‘]str4=str3.copy()print(str4)#[[1, 2], ‘jiaxin‘, ‘john‘]str4[1]="jiaxin01"print(str3)     #str3不变，str4改变print(str4)# [[1, 2], ‘jiaxin‘, ‘john‘]# [[1, 2], ‘jiaxin01‘, ‘john‘]

Shallow copy:

str5=[[1,2],"jiaxin",‘john‘]str6=str5.copy()   #等价于str6=str5[:],但是不等于str6=str5  很重要！！！！print(str5)print(id(str5[0]))print(str6)print(id(str6[0]))# [[1, 2], ‘jiaxin‘, ‘john‘]# [[1, 2], ‘jiaxin‘, ‘john‘]str6[0][1]=201    #str5,str6一起改变print(str5)print(str6)# [[1, 201], ‘jiaxin‘, ‘john‘]# [[1, 201], ‘jiaxin‘, ‘john‘]

Deep copy

# -*-coding:utf-8 -*-__author__ = ‘xiaojiaxin‘__file_name__ = ‘deep_copy‘import copy#深拷贝需要一个独立的模块来完成a=[[1,2],3,4]b=copy.deepcopy(a)print(id(a))print(id(b))b[0][0]=99print(a)print(b)#1080515447944#1080515539400# [[1, 2], 3, 4]# [[99, 2], 3, 4]

Full assignment:
B=a situation

a=[[1,2],3,4]b=aprint(id(a))print(id(b))b[0][0]=99print(id(a))print(id(b))print(a)print(b)# 818876113416# 818876113416# 818876113416# 818876113416# [[99, 2], 3, 4]# [[99, 2], 3, 4]

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6.Python depth Copy