Numpy lexicographic ordering

Question

I\'d like to lexicographically sort the following array a (get index positions), but, I\'m having problems understanding the numpy results:

>>>         


        

Answer 1

The order of significance for keys is opposite to what you expected. In order to get expected result just flip the matrix upside down

>>> np.lexsort(np.flipud(a))
array([1, 4, 0, 2, 5, 3])