Numpy: Subtract 2 numpy arrays row wise

Question

I have 2 numpy arrays a and b as below:

a = np.random.randint(0,10,(3,2))
Out[124]: 
array([[0, 2],
       [6, 8],
       [0, 4]])
b = np.random.randint(0,10         


        

Answer 1

Just use np.newaxis (which is just an alias for None) to add a singleton dimension to a, and let broadcasting do the rest:

In [45]: a[:, np.newaxis] - b
Out[45]: 
array([[[-5, -7],
        [-2, -2]],

       [[ 1, -1],
        [ 4,  4]],

       [[-5, -5],
        [-2,  0]]])