6.Python深淺拷貝
阿新 • • 發佈：2018-02-09
str2 cto str sha ges mage process text pre Python深淺拷貝
變量賦值的過程：
# -*-coding:utf-8 -*-
__author__ = ‘xiaojiaxin‘
__file_name__ = ‘shallowcopy_deepcopy‘
#當拷貝數據足夠多的時候，浪費空間
# str1=[1,"jiaxin","john"]
# str2=[1,"jiaxin","john"]
# print(str1)
# print(str2)copy方法
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不變，str4改變 print(str4) # [[1, 2], ‘jiaxin‘, ‘john‘] # [[1, 2], ‘jiaxin01‘, ‘john‘]
淺拷貝：
str5=[[1,2],"jiaxin",‘john‘] str6=str5.copy() #等價於str6=str5[:],但是不等於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,str6一起改變 print(str5) print(str6) # [[1, 201], ‘jiaxin‘, ‘john‘] # [[1, 201], ‘jiaxin‘, ‘john‘]
深拷貝
# -*-coding:utf-8 -*-
__author__ = ‘xiaojiaxin‘
__file_name__ = ‘deep_copy‘
import copy
#深拷貝需要一個獨立的模塊來完成
a=[[1,2],3,4]
b=copy.deepcopy(a)
print(id(a))
print(id(b))
b[0][0]=99
print(a)
print(b)
#1080515447944
#1080515539400
# [[1, 2], 3, 4]
# [[99, 2], 3, 4]完全賦值：
B=a情況
a=[[1,2],3,4] b=a print(id(a)) print(id(b)) b[0][0]=99 print(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深淺拷貝