`numpy:diag_indices_from`

Signature

def diag_indices_from(arr)

Return the indices to access the main diagonal of an n-dimensional array.

See diag_indices for full details.

import numpy as np

✓

Create a 4 by 4 array.

a = np.arange(16).reshape(4, 4)
a

✓

array([[ 0,  1,  2,  3],
       [ 4,  5,  6,  7],
       [ 8,  9, 10, 11],
       [12, 13, 14, 15]])

Get the indices of the diagonal elements.

di = np.diag_indices_from(a)
di

✓

(array([0, 1, 2, 3]), array([0, 1, 2, 3]))

a[di]

✓

array([ 0,  5, 10, 15])

This is simply syntactic sugar for diag_indices.

np.diag_indices(a.shape[0])

✓

(array([0, 1, 2, 3]), array([0, 1, 2, 3]))