Numpy add one column to other columns and remove

Say I have an 2d numpy array like this

[[1,2,3],
 [4,5,6],
 [7,8,9]]

I then want to convert it to

[[3,4],
 [9,10],
 [15,16]]

This could be a variable number of columns, I want to add the first column to every other column and remove it as well afterwards.

>Solution :

a = a[..., [0]] + a[..., 1:]

The …is for this to work with N dimensional arrays

Means -> Sum the [0] column to all the columns after the first one.

If you are using just a matrix you can use:

a = a[:, [0]] + a[:, 1:]