Mesh Face Random Material Assigner (Blender)

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#
#  This program is free software; you can redistribute it and/or
#  modify it under the terms of the GNU General Public License
#  as published by the Free Software Foundation; either version 2
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#  This program is distributed in the hope that it will be useful,
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#  GNU General Public License for more details.
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# ##### END GPL LICENSE BLOCK #####

#
#
#  Author            : Tamir Lousky (tlousky@gmail.com)
#
#  Homepage(Wiki)    : http://biological3d.wordpress.com/
#
#  Start of project              : 2013-01-25 by Clemens Barth
#  Last modified                 : 2013-01-30
#
#  Acknowledgements
#  ================
#
#  Blender: Patrick Boelens (helpful tuts!), CoDEmanX (useful bmesh info on BA forums!)

bl_info = {
    "name"        : "Random Face Material Assigner",
    "author"      : "Tamir Lousky",
    "version"     : (1, 0, 0),
    "blender"     : (2, 65, 0),
    "category"    : "Materials",
    "location"    : "3D View >> Tools",
    "wiki_url"    : "http://bioblog3d.wordpress.com/2013/01/30/random-meshface-material-assigner",
    "download_url": "http://pastebin.com/download.php?i=TAntxkmR",
    "description" : "Assign random materials to mesh object faces."}

import bpy
import random
import bmesh

class random_mat_panel(bpy.types.Panel):
    bl_idname      = "randomFaceMatPanel"
    bl_label       = "Random Face Material Assigner"
    bl_space_type  = 'VIEW_3D'
    bl_region_type = 'TOOLS'
    bl_context     = 'objectmode'

    def draw( self, context):                # Draw panel UI elements #
        layout = self.layout                 # Reference to panel layout object

        props = context.scene.face_assigner  # Create reference material assigner property group

        col1 = layout.column()               # Create a column
        col1.label(text="Randomly assign materials to each face on the object")

        box = layout.box()                   # Draw a box
        col2 = box.column(align=True)        # Create a column
        col2.prop( props, "rand_seed"  )     # Create randomization seed property on column
        col2.label(text="use this field to filter materials by name")
        col2.prop( props, "mat_prefix" )     # And the material prefix property too

class rand_mat_assigner(bpy.types.PropertyGroup):

    def randomize( self, context ):
        """ function name: randomize
            description:   This function assigns a random material to each face on the selected
                           object's mesh, from its list of materials (filtered by the mat_prefix)
        """
        random.seed(self.rand_seed)   # Set the randomization seed

        all_materials = bpy.context.object.data.materials
        filtered_materials = []

        if self.mat_prefix != "":                       # IF the user entered a prefix
            for material in all_materials:              # Iterate over all the object's materials
                if self.mat_prefix in material.name:    # Look for materials with the prefix
                    filtered_materials.append(material) # And filter them in
        else:
            filtered_materials = all_materials          # If there's no prefix, use all materials

        no_of_materials = len(filtered_materials)       # Count all/filtered materials on object

        bpy.ops.object.mode_set(mode = 'EDIT')          # Go to edit mode to create bmesh
        ob = bpy.context.object

        bm = bmesh.from_edit_mesh(ob.data)              # Create bmesh object from object mesh

        for face in bm.faces:    # Iterate over all of the object's faces
            face.material_index = random.randint(0, no_of_materials - 1)  # Assign random material to face

        ob.data.update()                            # Update the mesh from the bmesh data
        bpy.ops.object.mode_set(mode = 'OBJECT')    # Return to object mode

        return {'FINISHED'}

    rand_seed = bpy.props.IntProperty(     # Randomization seed
        name="rand_seed",
        description="Randomization seed",
        update=randomize)
    mat_prefix = bpy.props.StringProperty( # Prefix to filter materials by
        name="mat_prefix",
        description="Material name filter",
        default="",
        update=randomize)

def register():
    bpy.utils.register_module(__name__)
    bpy.types.Scene.face_assigner = bpy.props.PointerProperty(type=rand_mat_assigner)

def unregister():
    bpy.utils.unregister_module(__name__)