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python深度拷贝和浅拷贝的差异

云上笔记 2022-02-18 阅读 58
# add a new element to orignal 1D list a

import copy 
a = [1, 2]
b = a 
c = a.copy() 
d = a[:]
e = list(a)
f = copy.copy(a)
g = copy.deepcopy(a) 

print("add a new element to orignal 1D list a")
a.append(3)

print("original a = ", a)
print("assign b = ", b)
print("built-in c = ", c) 
print("slice d = ", d) 
print("list() e = ", e) 
print("copy.copy() f = ", f) 
print("copy.deepcopy() g = ", g) 

# add a new element to orignal 1D list a
# original a =  [1, 2, 3]
# assign b =  [1, 2, 3]
# built-in c =  [1, 2]
# slice d =  [1, 2]
# list() e =  [1, 2]
# copy.copy() f =  [1, 2]
# copy.deepcopy() g =  [1, 2]


# change first element in original 1D list a
import copy

print("change first element in original 1D list a")
a = [1, 2]
b = a 
c = a.copy() 
d = a[:]
e = list(a)
f = copy.copy(a)
g = copy.deepcopy(a)
a[0] = 5

print("original a = ", a)
print("assign b = ", b)
print("built-in c = ", c) 
print("slice d = ", d) 
print("list() e = ", e) 
print("copy.copy() f = ", f) 
print("copy.deepcopy() g = ", g)

# change first element in original 1D list a
# original a =  [5, 2]
# assign b =  [5, 2]

# built-in c =  [1, 2]
# slice d =  [1, 2]
# list() e =  [1, 2]
# copy.copy() f =  [1, 2]
# copy.deepcopy() g =  [1, 2]



# add a new element to orignal 2D list a

import copy 

a = [[1, 2], [3, 4]]
b = a  # 终生绑定
c = a.copy()  #暂时绑定
d = a[:]   # 一维  deepcopy   二维 shallow copy
e = list(a)
f = copy.copy(a)
g = copy.deepcopy(a) 

print("add a new element to orignal 2D list a")

print("idx_a:",id(a))
print("idx_d:",id(d))
a.append([5, 6])
a[0][1] = 999
print("idx_a:",id(a))
print("idx_d:",id(d))

print("original a = ", a)
print("assign b = ", b)
print("built-in c = ", c) 
print("slice d = ", d) 
print("list() e = ", e) 
print("copy.copy() f = ", f) 
print("copy.deepcopy() g = ", g)

# add a new element to orignal 2D list a
# original a =  [[1, 2], [3, 4], [5, 6]]
# assign b =  [[1, 2], [3, 4], [5, 6]]

# built-in c =  [[1, 2], [3, 4]]
# slice d =  [[1, 2], [3, 4]]
# list() e =  [[1, 2], [3, 4]]
# copy.copy() f =  [[1, 2], [3, 4]]
# copy.deepcopy() g =  [[1, 2], [3, 4]]

# add a new element to orignal 2D list a
# idx_a: 140448613644544
# idx_d: 140448613505216
# idx_a: 140448613644544
# idx_d: 140448613505216
# original a =  [[1, 999], [3, 4], [5, 6]]
# assign b =  [[1, 999], [3, 4], [5, 6]]

# built-in c =  [[1, 999], [3, 4]]
# slice d =  [[1, 999], [3, 4]]
# list() e =  [[1, 999], [3, 4]]
# copy.copy() f =  [[1, 999], [3, 4]]
# copy.deepcopy() g =  [[1, 2], [3, 4]]



# change first element in original 2D list a
print("change first element in original 2D list a")
a = [[1, 2], [3, 4]]
b = a 
c = a.copy() 
d = a[:]
e = list(a)
f = copy.copy(a)
g = copy.deepcopy(a) 

print("idx_a:",id(a))
print("idx_d:",id(d))
a[0][0] = 5
print("idx_a:",id(a))
print("idx_d:",id(d))

print("original a = ", a)
print("assign b = ", b)
print("built-in c = ", c) 
print("slice d = ", d) 
print("list() e = ", e) 
print("copy.copy() f = ", f) 
print("copy.deepcopy() g = ", g)


# original a =  [[5, 2], [3, 4]]
# assign b =  [[5, 2], [3, 4]]
# built-in c =  [[5, 2], [3, 4]]
# slice d =  [[5, 2], [3, 4]]
# list() e =  [[5, 2], [3, 4]]
# copy.copy() f =  [[5, 2], [3, 4]]
# copy.deepcopy() g =  [[1, 2], [3, 4]]

疑问:list赋值和append操作会造成不一样的结果?

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