insert empty at selected vertices of a mesh, mesh must be back in object mode

insert_empty_at_world_location.py

# must select 3 verts.

import bpy
#from mathutils import Vector, Quaternion

ob = bpy.context.object

# needs to be in object mode to check the status, i think?
# check if 3 verts selected.
selected_idx = [i.index for i in ob.data.vertices if i.select]
print(len(selected_idx))
print(selected_idx)


# get vertex locations
# ob.matrix_world = full matrix.
world_coordinates = []
for idx in selected_idx:
    point = ob.data.vertices[idx].co   # local
    world_coord = ob.matrix_world * point
    bpy.ops.object.add(type='EMPTY', location=world_coord, rotation=(0, 0, 0))