How do I select all objects without materials applied?

Question

I have a complex scene with CAD exported files and other meshes. There is a big amount of objects (> 200) and many of them are missing a material.

How do I select all the objects with no material so that I can apply one to them without affecting the other objects?

Shift+L + Material does not work because these objects do no share the same material.

Answer 1

An automated way to do this is using python. What you do is deselecting all objects and then iterating through every object to see if it has a material. Then you select all the objects without a material.

#import the blender python module
import bpy

#deselect all objects
bpy.ops.object.select_all(action='DESELECT')

#looking through all objects
for obj in bpy.data.objects:
    #if the object is a mesh and not a lamp or camera etc.
    if obj.type == 'MESH':
        #looking through every material slot
        for slot in obj.material_slots:
            #if there's no material slot
            if slot.material == None:
                #select the object
                obj.select = True

You have to paste it into Blender's text editor and then hit Run Script at the bottom of the editor.

Answer 2

While you can select a material'd object and do Select > Linked > Material to select objects with the same material, I don't know how to automagically select non-material'd objects, so here's a work-around:

Select your material'd objects, them move them to another layer M, 2 (or whatever layer number you want). Once you have all the material'd objects on another layer, you'll be left with a layer full of non-material'd objects (and maybe a camera and some lights). At that point, you can A to select the remaining non-material'd objects.

Answer 3

I've tried the palkonimo's script in Blender 2.78 and it didn't work. So I've modified it a bit:

#import the blender python module
import bpy

#deselect all objects
bpy.ops.object.select_all(action='DESELECT')

#looking through all objects
for obj in bpy.data.objects:
    #if the object is a mesh and not a lamp or camera etc.
    if obj.type == 'MESH':
        slots = obj.material_slots.keys()
        # select the object if there's no material slot 
        # or if there're empty material slots
        obj.select = not ( slots and all( slot for slot in slots ) )

Answer 4

import bpy
bpy.ops.object.select_all(action='DESELECT')

for obj in bpy.context.view_layer.objects:
    if obj.type == 'MESH':
        for slot in obj.material_slots:
            if slot.material == None:
                obj.select_set(True)

This would be my version of the script working in 2.92

Answer 5

Make an array of objects with no materials:

import bpy

no_mat_objects = []

for obj in bpy.data.objects:
    if obj.type == 'MESH' and not obj.data.materials:
        no_mat_objects.append(obj)

bpy.context.view_layer.objects.active = no_mat_objects[0]
for obj in no_mat_objects:
    obj.select_set(True)
```