How do I make an addon from this code?

Question

I have this piece of code that I am using to remove duplicate materials. What I do is I open the Text Editor, paste it in and click Run Script. I would like to make it a Tools Shelf button. This is the code:

import bpy

mat_list = bpy.data.materials

for o in bpy.data.objects:
    for s in o.material_slots:
        if s.material.name[-3:].isnumeric():
            # the last 3 characters are numbers
            if s.material.name[:-4] in mat_list:
                # there is a material without the numeric extension so use it
                s.material = mat_list[s.material.name[:-4]]

I tried following the instructions here, but I get this error:

This is my first time messing around with Blender scripts, any help appreciated!

EDIT: This is my complete addon:

import bpy

bl_info = {
 "name": "Remove Duplicate Materials",
 "author": "Me",
 "version": (1, 0, 0),
 "blender": (2, 7, 8),
 "location": "3D View > Tool Shelf > My Tools",
 "description": "Remove duplicate materials",
 "warning": "",
 "wiki_url": "",
 "tracker_url": "",
 "category": "User"}

import bpy

mat_list = bpy.data.materials

for o in bpy.data.objects:
    for s in o.material_slots:
        if s.material.name[-3:].isnumeric():
            # the last 3 characters are numbers
            if s.material.name[:-4] in mat_list:
                # there is a material without the numeric extension so use it
                s.material = mat_list[s.material.name[:-4]]

Answer 1

Maybe try this and see if it makes sense to you. It really should also poll to see if objects are selected in the operator.

bl_info = {
"name": "Material Button Panel",
"author": "Your Name Here",
"version": (1, 0),
"blender": (2, 78, 0),
"location": "View3D > Toolbar",
"description": "Button to Remove Duplicate MAterials",
"warning": "",
"wiki_url": "",
"category": "Material",
}


import bpy



class RemoveDupmatl(bpy.types.Operator):
    """Remove Duplicate Materials"""
    bl_idname = "object.remove_dupmatl"


    bl_label = "Remove Duplicate Materials"
    bl_options = { 'REGISTER', 'UNDO' }

    def execute(self, context):

        scene = context.scene


        #new code
        mat_list = bpy.data.materials

        for o in bpy.data.objects:
            for s in o.material_slots:
                if s.material.name[-3:].isnumeric():
                    # the last 3 characters are numbers
                    if s.material.name[:-4] in mat_list:
                        # there is a material without the numeric extension so use it
                        s.material = mat_list[s.material.name[:-4]]

        return {'FINISHED'}






class TestPanel(bpy.types.Panel):
    """A custom panel in the viewport toolbar"""
    bl_label = "Test Panel"
    bl_space_type = 'VIEW_3D'
    bl_region_type = 'TOOLS'
    bl_category = "Tests"

    def draw(self, context):
        layout = self.layout

        row = layout.row()

        row.label(text="Single Button")
        row = layout.row()
        row.operator("object.remove_dupmatl", text = "Remove Dup Material", icon = 'ROTACTIVE')








def register():
    bpy.utils.register_class(RemoveDupmatl)
    bpy.utils.register_class(TestPanel)


def unregister():
    bpy.utils.unregister_class(RemoveDupmatl)
    bpy.utils.unregister_class(TestPanel)




if __name__ == "__main__":
    register()