Deep copy and shallow copy of Python

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Both the numbers and the memory in the string point to the same address, so deep copies and shallow copies are meaningless to them.

Import Copya = 123                #赋值print (ID (a))           #输出存储变量的地址b = Aprint (ID (b)) B = Copy.copy (a)       #浅拷贝print (ID (b)) C = Copy.deepcopy (a)  #深拷贝print (ID (c))

　

Shallow copy

For dictionary tuples and lists, the address of the memory is different when a shallow copy and a deep copy are made

A shallow copy copies only the first layer of data in memory

Import copydic = {' Key1 ': 123, ' Key2 ': [123,456]}            #创建一个字典嵌套列表print (ID (dic[' key1 '])) print (ID (dic[' key2 ')) print ( ID (dic[' key2 '][0]))                      #打印列表中的地址print ("\ n") New_dic = Copy.copy (DIC)                       #使用浅拷贝赋值 print ("*", ID (new_dic[' key1 ')) Print ("*", ID (new_dic[' key2 ')) print ("*", ID (new_dic[' key2 '][0]))

Find the value of an in-memory address is exactly the same

Deep Copy & nbsp                          ,         &NB Sp                          ,         &NB Sp                          ,         &NB Sp                          ,         &NB Sp                          ,         &NB Sp                                 span>  

And for a deep copy, all the data will be recreated.

Import copydic = {' Key1 ': 123, ' Key2 ': [123,456]}            #创建一个字典嵌套列表print (ID (dic[' key1 '])) print (ID (dic[' key2 ')) print ( ID (dic[' key2 '][0]))                      #打印列表中的地址print ("\ n") New_dic = Copy.deepcopy (DIC)                       #使用深拷贝赋值 print ("*", ID (new_dic[' key1 ') ]) Print ("*", ID (new_dic[' key2 ')) print ("*", ID (new_dic[' key2 '][0]))

Application of deep-shade copy

In a shallow copy, the value of the copied object changes when the value of the copied object is changed.

ImportCopydic= {'Key1': 123,'Key2': [123,456]}#Create a dictionary nested listPrint(dic['Key2'][0])#Print the address in the listPrint("\ n") New_dic= Copy.deepcopy (DIC)#use a shallow copy to assign a valuenew_dic['Key2'][0] = 789#change the value of a list in a dictionaryPrint(dic['Key2'][0])Print((new_dic['Key2'][0]))

Deep copy should be used when you do not want to change the copied value

ImportCopydic= {'Key1': 123,'Key2': [123,456]}#Create a dictionary nested listPrint(dic['Key2'][0])#Print the address in the listPrint("\ n") New_dic= Copy.deepcopy (DIC)#assigning values using deep copiesnew_dic['Key2'][0] = 789#change the value of a list in a dictionaryPrint(dic['Key2'][0])Print((new_dic['Key2'][0]))

　Shallow copy deep copy deep copy

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Deep copy and shallow copy of Python