Python Matrix Question: How do I make the right top, left top, right bottom, left bottom only 1 and the rest zero?

>>> import numpy as np
>>> a = np.zeros((3, 3))
>>> a
array([[0., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.]])
>>> a[0,0] = 1
>>> a
array([[1., 0., 0.],
       [0., 0., 0.],
       [0., 0., 0.]])
>>> a[-1, 0] = 1
>>> a
array([[1., 0., 0.],
       [0., 0., 0.],
       [1., 0., 0.]])
>>> a[0, -1] = 1
>>> a
array([[1., 0., 1.],
       [0., 0., 0.],
       [1., 0., 0.]])
>>> a[-1, -1] = 1
>>> a
array([[1., 0., 1.],
       [0., 0., 0.],
       [1., 0., 1.]])