What is the fastest way to map group names of numpy array to indices?

Question

I\'m working with 3D pointcloud of Lidar. The points are given by numpy array that looks like this:

points = np.array([[61651921, 416326074, 39805], [6160525         


        

Answer 1

You might just iterate and add the index of each element to the corresponding list.

from collections import defaultdict

res = defaultdict(list)

for idx, elem in enumerate(cubes):
    #res[tuple(elem)].append(idx)
    res[elem.tobytes()].append(idx)

Runtime can be further improved by using tobytes() instead of converting the key to a tuple.