Scripting for Artists: Creating your own Add-ons

  • So far: code in blend file
  • Absolutely fine if the code should be there. For example one-off things for that particular blender scene. Rigify also uses this.
  • Hard to reuse.
  • Hard to distribute.
  • Solution: add-ons.

What is an add-on?

  • Python code in file on disk, rather than buried inside a blend file.
  • Just a text file, you can open it with any text editor.
  • Blender's text editor works too, but I always get confused like that. Are you editing a text file on disk, or a text datablock in the blend file? Saving with Ctrl+S or Alt+S.
  • Use a free text editor, like Visual Studio Code, Atom, Notepad++.
  • On Windows, avoid Notepad. Even though Python is text, Notepad doesn't support files from Linux and thus you can have trouble reading code from Blender itself, or other people's add-ons.
  • PyCharm works for bigger projects, but the smarter your editor the more work you need to do to remove all the error markers.
  • Naming: recommended lower case, letters without accents, numbers, and underscores only. And end in .py.

Location of add-ons:

import addon_utils
  • More info:
    • Help
    • Manual
    • Advanced
    • Scripting & Extending Blender
    • Lots of info there, including Add-on Tutorial

Ingredients of a simple Add-on

  • Starts with some metadata in bl_info, like name of the add-on, the version number, version of Blender that's compatible with it, authors, etc.
  • register and unregister functions.
  • Then code just like we're used to.
  • Can be enabled & disabled in user preferences.

Minimal add-on:

bl_info = {
    "name": "My Test Add-on",
    "blender": (2, 83, 0),
    "category": "Object",
def register():
    print("Hello World")
def unregister():
    print("Goodbye World")

Dictionary: already seen in chapter 5. Basically a lookup table, bl_info["name"] gives "My Test Add-on".

  • Save in random directory, name
  • Start Blender, user prefs, install, enable & disable add-on and check console.
  • Now you know why in the previous chapter we had an unregister() function, even though it wasn't used yet.
  • Was saved by Blender in $HOME/.config/2.83/scripts/addons/, Blender made the right directories for us.
  • Now open the installed file in your editor so you can keep editing and reloading. (what happens on reload we'll cover in a few minutes)

Monkey Grid Add-on

  • Add bl_info
  • Copy code from previous chapter
  • Save & reload scripts
  • Done!

Accessing add-on from within Blender

import my_first_addon

# change the print statements for both register & unregister.


import importlib
my_first_addon = importlib.reload(my_first_addon)


Making code usable by others (maybe skip this part)

  • Operators are glue between menus, buttons, and the code to run.
  • Avoid calling operators from Python code. Sometimes unavoidable, and that's fine.
  • Put monkey grid generation code into a function.
  • Call that function from the operator.
  • Call that function from the console.


  • Code is just text in files.
  • Single-file add-on. Multi-file is not much different, but won't cover here. Requires trick with reloading; look at how other add-ons are doing it.
  • Add-on requires bl_info and register/unregister functions.
  • Put one or more operators there.
  • Later video: making a user interface