A Blender Python script that draws text next to the verts of a active mesh

draw_text_on_the_verts_of_a_mesh.py

import bpy
import blf

from bpy_extras.view3d_utils import location_3d_to_region_2d


def draw_text_on_verts():
    font_id = 0
    region = bpy.context.region
    rv3d = bpy.context.space_data.region_3d

    for vert in bpy.context.active_object.data.vertices:

        # get the location of the vert on the Viewport
        coord = vert.co
        matrix_world = bpy.context.active_object.matrix_world
        vector3d = matrix_world @ coord
        x, y = location_3d_to_region_2d(region, rv3d, vector3d)

        # draw text
        blf.position(font_id, x, y, 0)
        blf.size(font_id, 20, 72)
        blf.color(font_id, 0.8, 0.0, 0.0, 1.0)
        blf.draw(font_id, f"{vert.index} Hello Word")


def draw_text_callback():
    if bpy.context.active_object.type == "MESH":
        draw_text_on_verts()


def main():
    run = True

    if run:
        handle = bpy.types.SpaceView3D.draw_handler_add(draw_text_callback, (), "WINDOW", "POST_PIXEL")

        # save the handle so we can cleanup when `run` is set to False
        bpy.types.Scene.draw_text_on_verts_handle_ref = handle
    else:
        if (
            # make sure draw_text_on_verts_handle_ref exists in the bpy.types.Scene
            hasattr(bpy.types.Scene, "draw_text_on_verts_handle_ref")
            and bpy.types.Scene.draw_text_on_verts_handle_ref is not None
        ):
            bpy.types.SpaceView3D.draw_handler_remove(bpy.types.Scene.draw_text_on_verts_handle_ref, "WINDOW")
            bpy.types.Scene.draw_text_on_verts_handle_ref = None


if __name__ == "__main__":
    main()