Sorting arrays in NumPy ascending on one column and descending on other column

Question

How can I sort 2d array in NumPy by the 1st column ascending and 2nd column descending?

For example,

a = array([[9, 2, 3],
           [4, 5, 6],
           [7, 0, 5],
           [7, 1, 6]])

Result :

array([[4, 5, 6],
       [7, 1, 6],
       [7, 0, 5],
       [9, 2, 3]])

this might help you: https://stackoverflow.com/questions/4233476/sort-a-list-by-multiple-attributes — PandaBlue, Oct 11 '19 at 06:56

score 4 · Accepted Answer · answered Oct 11 '19 at 07:29

You can use the np.lexsort function for this

import numpy as np
a = np.asarray([[9, 2, 3],
           [4, 5, 6],
           [7, 0, 5],
           [7, 1, 6]])

a[np.lexsort((-a[:, 1], a[:, 0]))]

Output

array([[4, 5, 6],
       [7, 1, 6],
       [7, 0, 5],
       [9, 2, 3]])

1 Answers1