Python基礎 day6 深淺拷貝

列表的copy方法：

s = [1,'yuyang','dba']

s1 = s.copy()
print(s1)
s1[0] = 2
print(s)
print(s1)

[1, 'yuyang', 'dba']

[1, 'yuyang', 'dba']
[2, 'yuyang', 'dba']
process finished with exit code 0

s = [[1,2],'yuyang','dba']

s1 = s.copy()
或者s1 = s[:]

s = [[1,2],'yuyang','dba']

s1 = s.copy()
print(s)
print(s1)
s1[0][1] = 3
print(s1)
print(s)

[[1, 2], 'yuyang', 'dba']

[[1, 2], 'yuyang', 'dba']
[[1, 3], 'yuyang', 'dba']
[[1, 3], 'yuyang', 'dba']
process finished with exit code 0

s1 = s                        #兩個變數完全相等

s1[1] = 'zhangsan'            #修改s1的乙個元素

print(s)

print(s1)                     #從列印結果中來看，是兩個都被修改了的

s2 = s[:]                     #s2淺拷貝s

s2[2] = 'pm'                 #修改s2中乙個元素

print(s)

print(s1)

print(s2)                     #從列印結果中看，原來兩個變數(列表沒有被修改，只有淺拷貝的s2自己修改了，這裡就體現出做淺拷貝和=的區分)

執行結果：

[[1, 2], 'zhangsan', 'dba']

[[1, 2], 'zhangsan', 'dba']
[[1, 2], 'zhangsan', 'dba']
[[1, 2], 'zhangsan', 'dba']
[[1, 2], 'zhangsan', 'pm']
process finished with exit code 0

ctrl + /

print('step1'.center(30,'-'))

a = 1
b = a
print(a)
print(b)
print('---')
print(id(a))
print(id(b))
print('step2'.center(30,'-'))
b = 2
print(a)
print(b)
print('---')
print(id(a))
print(id(b))
print('step3'.center(30,'-'))
a = [1,2]
b = a
print(a)
print(b)
print('---')
print(id(a))
print(id(b))
print('step4'.center(30,'-'))
b[1] = 3
print(a)
print(b)
print('---')
print(id(a))
print(id(b))

------------step1-------------11

---1767416928
1767416928
------------step2-------------12
---1767416928
1767416960
------------step3-------------
[1, 2]
[1, 2]
---1365916817416
1365916817416
------------step4-------------
[1, 3]
[1, 3]
---1365916817416
1365916817416
process finished with exit code 0

import copy

s = [[1,2],'yuyang','dba']
s1 = copy.deepcopy(s)
print(s1)

[[1, 2], 'yuyang', 'dba']

process finished with exit code 0

import copy

s = [[1,2],'yuyang','dba']
print(s)
s1 = copy.deepcopy(s)         #深拷貝
s2 = s.copy()                 #淺拷貝
#s2 = copy.copy(s)            #也是淺拷貝和上一行的執行結果一致
s1[0][1] = 3
s2[0][1] = 4
print(s)
print(s1)
print(s2)

[[1, 2], 'yuyang', 'dba']

[[1, 4], 'yuyang', 'dba']
[[1, 3], 'yuyang', 'dba']
[[1, 4], 'yuyang', 'dba']
process finished with exit code 0

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