How to add an extra column to a NumPy array

Question

Let’s say I have a NumPy array, a:

a = np.array([
    [1, 2, 3],
    [2, 3, 4]
    ])

And I would like to add a column of ze

Answer 1

One way, using hstack, is:

b = np.hstack((a, np.zeros((a.shape[0], 1), dtype=a.dtype)))