I have those arrays:

a = np.array([[1,2],[3,4],[5,6],[7,8]])b = np.array([1,2,3,4])

and I want them to multiply like so:

[[1*1, 2*1],
[3*2, 4*2],
[5*3, 6*3],
[7*4, 8*4]]

... basically out[i] = a[i] * b[i], where a[i].shape is (2,) and b[i] then is a scalar.

What's the trick? np.multiply seems not to work:

>>> np.multiply(a, b)
ValueError: operands could not be broadcast together with shapes (4,2) (4)

add an axis to b:

>>> np.multiply(a, b[:, np.newaxis])
array([[ 1,  2],[ 6,  8],[15, 18],[28, 32]])