Indexing one array by another in numpy

Question

Suppose I have a matrix A with some arbitrary values:

array([[ 2, 4, 5, 3],
       [ 1, 6, 8, 9],
       [ 8, 7, 0, 2]])

A

Answer 1

More recent versions have added a take_along_axis function that does the job:

In [203]: A = np.array([[ 2, 4, 5, 3], 
     ...:        [ 1, 6, 8, 9], 
     ...:        [ 8, 7, 0, 2]])                                                
In [204]: B = np.array([[0, 0, 1, 2], 
     ...:        [0, 3, 2, 1], 
     ...:        [3, 2, 1, 0]])                                                 
In [205]: np.take_along_axis(A,B,1)                                             
Out[205]: 
array([[2, 2, 4, 5],
       [1, 9, 8, 6],
       [2, 0, 7, 8]])

There's also a put_along_axis.