add a new column to numpy array

import numpy as np
N = 10
a = np.random.rand(N,N)
b = np.zeros((N,N+1))
b[:,:-1] = a

np.concatenate((np.zeros((3,3), dtype=int), arr), axis=1)
array([[0, 0, 0, 1, 2, 3],
       [0, 0, 0, 4, 5, 6],
       [0, 0, 0, 7, 8, 9]])