Index a 2D Numpy array with 2 lists of indices

Question

I\'ve got a strange situation.

I have a 2D Numpy array, x:

x = np.random.random_integers(0,5,(20,8))

And I have 2 indexers--one w

Answer 1

import numpy as np
x = np.random.random_integers(0,5,(4,4))
x
array([[5, 3, 3, 2],
       [4, 3, 0, 0],
       [1, 4, 5, 3],
       [0, 4, 3, 4]])

# This indexes the elements 1,1 and 2,2 and 3,3
indexes = (np.array([1,2,3]),np.array([1,2,3]))
x[indexes]
# returns array([3, 5, 4])

Notice that numpy has very different rules depending on what kind of indexes you use. So indexing several elements should be by a tuple of np.ndarray (see indexing manual).

So you need only to convert your list to np.ndarray and it should work as expected.