Blender: Find Unweighted Vertices

select_unweighted_verts.py

# by Razgriz
# Select Unweighted Vertices on a Mesh
# 
# To Use:
# Open Scripting Workspace (tab at top)
# Create a new script
# Paste script content in text editor
# Select Object in object mode
# Run script

import bpy

object = bpy.context.active_object.data
verts = object.vertices
color_map_collection = object.vertex_colors

unweighted_verts = []

# Loop across polygons and verts
for poly in object.polygons:
    for idx in poly.loop_indices:
        v = object.loops[idx].vertex_index
        if len(verts[v].groups) == 0:
            unweighted_verts.append(verts[v].index)

if len(unweighted_verts) > 0:
    print("Unweighted Verts Found")
    bpy.ops.object.mode_set(mode = 'EDIT') 
    bpy.ops.mesh.select_mode(type="VERT")
    bpy.ops.mesh.select_all(action = 'DESELECT')
    bpy.ops.object.mode_set(mode = 'OBJECT')
    for vid in unweighted_verts:
        object.vertices[vid].select = True
    bpy.ops.object.mode_set(mode = 'EDIT')
    for area in bpy.context.screen.areas: # zoom to selected
        if area.type == 'VIEW_3D':
            ctx = bpy.context.copy()
            ctx['area'] = area
            ctx['region'] = area.regions[-1]
            bpy.ops.view3d.view_selected(ctx)            # points view
else:
    print("No Unweighted Verts Found")