Blender addon to rename selected MMD models' armature, mesh, and materials to match the name of the empty. https://twitter.com/maxkagamine/status/1380531111906869248

batch_rename_mmd_models.py

# MIT License
#
# Copyright (c) 2021 Max Kagamine
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.

import bpy
import re

bl_info = {
    'name': 'Batch Rename MMD Models',
    'author': 'Max Kagamine',
    'version': (1, 0),
    'blender': (2, 91, 0),
    'location': 'F3 > Batch Rename MMD Models',
    'description': "Renames selected MMD models' armature, mesh, and materials to match the name of the empty.",
    'category': 'Object',
    'wiki_url': 'https://gist.github.com/maxkagamine/a8315bf3a3c2d36892c5ca2c1761c85c',
}

ARMATURE_SUFFIX = '_arm'
MESH_SUFFIX = '_mesh'

class OBJECT_OT_BatchRenameMmdModels(bpy.types.Operator):
    """
    Renames selected MMD models' armature, mesh, and materials to match the name of the empty.
    """
    bl_idname = 'object.batch_rename_mmd_models'
    bl_label = 'Batch Rename MMD Models'
    bl_options = {'UNDO'}

    @classmethod
    def poll(cls, context):
        return len(context.selected_objects) > 0

    def execute(self, context):
        changes_made = False

        for model in context.selected_objects:
            try:
                self.batch_rename(model)
                changes_made = True
            except ValueError as err:
                self.report({'ERROR'}, str(err))

        # This determines whether an undo entry should be created
        return {'FINISHED'} if changes_made else {'CANCELLED'}

    def batch_rename(self, model):
        # Check that the right thing is selected
        if model is None or model.type != 'EMPTY':
            raise ValueError(f'{model.name} is not an empty')

        # Get the armature and mesh
        armature = self.get_child(model, 'ARMATURE', ARMATURE_SUFFIX)
        mesh = self.get_child(armature, 'MESH', MESH_SUFFIX)

        # Armature should have the old name, in case materials are already prefixed
        old_model_name = armature.name[:-len(ARMATURE_SUFFIX)]

        # Rename objects
        armature.name = f'{model.name}{ARMATURE_SUFFIX}'
        armature.data.name = model.name
        mesh.name = f'{model.name}{MESH_SUFFIX}'
        mesh.data.name = model.name

        # Get unique materials
        materials = [slot.material for slot in mesh.material_slots if
            slot.material is not None and slot.material.users == 1]

        # Rename materials
        for material in materials:
            material_name = material.name

            # Remove old name if present
            if material_name.startswith(old_model_name):
                # Tfw there's a len() function but no rin()
                material_name = material_name[len(old_model_name) + 1:]

            # In case multiple models were imported with conflicting material names
            material_name = re.sub('\.\d+$', '', material_name)

            # Prefix with new model name
            material.name = f'{model.name} {material_name}'

    def get_child(self, obj, type, suffix):
        children = [x for x in obj.children if x.type == type and x.name.endswith(suffix)]

        if len(children) != 1:
            raise ValueError(f'{obj.name} does not contain a single {type} that ends in {suffix}')

        return children[0]

def menu_func(self, context):
    self.layout.operator('object.batch_rename_mmd_models')

def register():
    bpy.utils.register_class(OBJECT_OT_BatchRenameMmdModels)
    bpy.types.TOPBAR_MT_edit.append(menu_func)

def unregister():
    bpy.utils.unregister_class(OBJECT_OT_BatchRenameMmdModels)
    bpy.types.TOPBAR_MT_edit.remove(menu_func)

if __name__ == '__main__':
    register()