Adding Submatrix in Numpy without Loop

Question

Let's say I got this a = np.arange(9).reshape((3,3)) I want get a numpy array of [9,12,15] which is a result of

[0+3+6, 1+4+7, 2+5+8]

Answer 1

You can usenumpy.array.sum() function by passing the axis=0:

>>> a.sum(axis=0)
array([ 9, 12, 15])