我通常使用Python作为我的主要编程语言之一。
我观察到通过同时分配交换numpy 2d-array的行会覆盖元素。我觉得奇怪的是这种覆盖只发生在：
并且，没有发生：
（请参阅以下“案例1”结果。）
我想知道这种行为的机制。这是我的测试代码：
import numpy as np
def swap(seq):
'''swaps first two elemnts'''
print('Before swapping\n', seq)
seq[0], seq[1] = seq[1], seq[0]
print('After swapping\n', seq)
print('')
print('Case 1: array_2d')
array_2d = np.arange(8).reshape(4, 2)
swap(array_2d)
print('Case 2: list_of_list')
list_of_list = [[0, 1], [2, 3], [4, 5], [6, 7]]
swap(list_of_list)
print('Case 3: list_of_array')
list_of_array = [np.array([0, 1]),
np.array([2, 3]),
np.array([4, 5]),
np.array([6, 7])]
swap(list_of_array)
print('Case 4: array_1d')
array_1d = np.arange(4)
swap(array_1d)
print('Case 5: list_of_numbers')
list_of_numbers = list(range(4))
swap(list_of_numbers)
结果是：
Case 1: array_2d
Before swapping
[[0 1]
[2 3]
[4 5]
[6 7]]
After swapping
[[2 3] # <- failed to swap
[2 3] # <- failed to swap
[4 5]
[6 7]]
Case 2: list_of_list
Before swapping
[[0, 1], [2, 3], [4, 5], [6, 7]]
After swapping
[[2, 3], [0, 1], [4, 5], [6, 7]]
Case 3: list_of_array
Before swapping
[array([0, 1]), array([2, 3]), array([4, 5]), array([6, 7])]
After swapping
[array([2, 3]), array([0, 1]), array([4, 5]), array([6, 7])]
Case 4: array_1d
Before swapping
[0 1 2 3]
After swapping
[1 0 2 3]
Case 5: list_of_numbers
Before swapping
[0, 1, 2, 3]
After swapping
[1, 0, 2, 3]
我发现以下帖子涉及同时分配，但仍无法理解上述行为。
使用.copy()方法的解决方案。
同时转让的评估顺序。
我很欣赏任何提示。
感谢。