在numpy数组中交换两个整数会导致IndexError

Question

我第一次尝试Swap two values in a numpy array.

但是这个看似简单的问题会导致索引错误或错误的结果，所以我必须做错了什么……但是什么呢？

import numpy as np

# Swap 1 and 3, leave the 0s alone!
i = np.array([1, 0, 1, 0, 0, 3, 0, 3])

# Swaps incorrectly
i[i==1], i[i==3] = 3, 1

# IndexError
i[i==1, i==3] = i[i==3, i==1]

# IndexError
i[[i==1, i==3]] = i[[i==3, i==1]]

# IndexError
ix1 = np.argwhere(i==1)
ix3 = np.argwhere(i==3)
i[[ix1, ix3]] = i[[ix3, ix1]]

# Swaps incorrectly
i[np.argwhere(i==1)], i[np.argwhere(i==3)] = 3, 1

Answer 1

>>> import numpy as np
>>> i = np.array([1, 0, 1, 0, 0, 3, 0, 3])
>>> i
array([1, 0, 1, 0, 0, 3, 0, 3])
>>> a, b = i ==3, i == 1  # save the indices
>>> i[a], i[b] = 1, 3
>>> i
array([3, 0, 3, 0, 0, 1, 0, 1])

Answer 2

您使用元组交换来交换值。对于numpy数组来说，这不是最安全的方法。 您的问题的答案已经发布。

https://stackoverflow.com/a/14933939/11459926