[FIXED] How to subtract arrays by only column python?

Issue

I have 2D array

 [1, 5],
 [2, 7],
 [3, 9] 

I want to result the array

 [1, 5],
 [2, 2],
 [3, 2] 

which is achieved by subtracting only columns and keeping the row as its. (7-5) (9-7)

I tried this below but im not able to get the proper output

import numpy as np

timeline = np.array([[1,5],
                     [2,7],
                     [3,9]]) 

def non_adjacent_diff(row):
    not_zero_index = np.where(row != 0)
    diff = row[not_zero_index][1:] - row[not_zero_index][:-1]
    np.put(row, not_zero_index[0][1:], diff)
    return row

np.apply_along_axis(non_adjacent_diff, 1, timeline)

print(timeline)

Solution

You can try this solution:

timeline[1:,-1] = np.diff(timeline[:,-1], axis=0)

Answered By - MSS