# concatenate 2 numpy arrays: row-wise >np.concatenate((array2D_1, array2D_2)) array([[ 0, 1, 2], [ 3, 4, 5], [ 6, 7, 8], [10, 11, 12], [13, 14, 15], [16, 17, 18]])
[1,2,3] + [4,5,6] # [1,2,3,4,5,6]