My variable changes (though I don't want to) once I change the other variable I used to set it up

I have these two arrays

x = np.array([[1, 0],
       [0, 1],
       [0, 0],
       [0, 0],
       [0, 0]])
z = np.array([[0, 0],
       [0, 0],
       [1, 0],
       [0, 1],
       [0, 0]])

and I wanted to switch the first column of these two.

target = 0
tempx = x[:, target]
tempz = z[:, target]
'''
but once I do this
'''
z[:, target] = tempx

it changed "tempz" although I did not do nothing with it except "z"!

Why is this happening and how can I change my code so that it switches columns?

I expected no change in "tempz" and "tempx" just because I changed "z" and "x". Was this a wrong assumption?

You can use numpy.copy: https://numpy.org/doc/stable/reference/generated/numpy.copy.html the documentation also mentions the problem you're having. You're not copying the array, but creating a reference to it! So changing the original also alters the reference.

To switch the first column of the two arrays without affecting each other, you need to make a copy of the columns.

import numpy as np

x = np.array([[1, 0],
              [0, 1],
              [0, 0],
              [0, 0],
              [0, 0]])
z = np.array([[0, 0],
              [0, 0],
              [1, 0],
              [0, 1],
              [0, 0]])

target = 0
tempx = np.copy(x[:, target])
tempz = np.copy(z[:, target])

z[:, target] = tempx
x[:, target] = tempz

print("x:")
print(x)
print("z:")
print(z)

In numpy, when you slice an array, it returns a view of the original array instead of creating a copy. For example, the below code will return the view of the z array and when you make a change to the either array (tempz and z), the original array will be modified.

tempz = z[:, target]

As other people have already pointed out, if you want to make change to only the specified array, you can use 'numpy.copy' function. It will create a new array which is independent of 'z' and will not affected by any modifications to the 'z'

I found this! article helpful.