Why does this not work for inverting a 2-D square array?

Question

I'm trying to invert (transpose) a 2-D square array in python. I know there are ways to do this with numpy, but since I have just a square array, I thought it could be simply done with the following:

array = [[1,2,3],[4,5,6],[7,8,9]]

invert = array

for i in range(len(array)):
    for j in range(len(array[0])):
        invert[j][i] = array[i][j]

However, when I run this and print the result, I get the following array

[1, 2, 3]
[2, 5, 6]
[3, 6, 9]

It seems to be partially inverted (first column is first row), but not fully (first row is still first row).

The code is very simple, I just start with inverse being the same as array, and then replace all inverse[j,i] with array[i,j]. Not sure why this doesn't work

Answer 1

Just correct your second line :

invert = [[0, 0, 0], [0, 0, 0], [0, 0, 0]]

In your case, the 2 lists invert and array correspond to the same element and are modified simultaneously.