Module API_intro

The Blender Python API Reference

Top Module:

Blender (*)

Submodules:

Armature
- Bone
- NLA
BGL
Camera (*)
Curve (*)
Draw (*)
Effect
Image (*)
Ipo (*)
Lamp (*)
Lattice
Library
Material (*)
Mathutils
Metaball (*)
NMesh
Noise
Object (*)
Registry
Scene (*)
- Radio (new)
- Render
Text
Texture (*)
Types
Window (* important: Window.EditMode)
World (*)
sys (*)

(*) - marks updated.

Introduction:

This reference documents the Blender Python API, a growing collection of Python modules (libraries) that give access to part of the program's internal data and functions.

Through scripting Blender can be extended in real-time via Python, an impressive high level, multi-paradigm, open source language. Newcomers are recommended to start with the tutorial that comes with it.

This opens many interesting possibilities, ranging from automating repetitive tasks to adding new functionality to the program: procedural models, importers and exporters, even complex applications and so on. Blender itself comes with some scripts, but many others can be found in the Scripts & Plugins sections and forum posts at the Blender-related sites listed below.

Scripting and Blender:

There are four basic ways to execute scripts in Blender:

They can be loaded or typed as text files in the Text Editor window, then executed with ALT+P.
Via command line: 'blender -P <scriptname>' will start Blender and executed the given script. <scriptname> can be a filename in the user's file system or the name of a text saved in a .blend Blender file: 'blender myfile.blend -P textname'.
Properly registered scripts can be selected directly from the program's menus.
Scriptlinks: these are also loaded or typed in the Text Editor window and can be linked to objects, materials or scenes using the Scriptlink buttons tab. Script links get executed automatically when their events (ONLOAD, REDRAW, FRAMECHANGED) are triggered. Normal scripts can create (Text) and link other scripts to objects and events, see Object.Object.addScriptLink, for example.

Registering scripts:

To be registered a script needs two things:

be either in the default scripts dir or in the user defined scripts path (see Info window, paths tab);
have a proper header.

Try 'blender -d' to know where your default dir for scripts is, it will inform either the dir or the file with that info already parsed, which is in the same dir of the scripts folder.

The header should be like this one (all double and single apostrophes below are required):

#!BPY
"""
Name: 'Script Name'
Blender: 233
Group: 'Export'
Submenu: 'All' all
Submenu: 'Selected' sel
Submenu: 'Configure (gui)' gui
Tooltip: 'Export to some format.'
"""

where:

Name is the string that will appear in the menu;
Blender is the minimum program version required to run the script;
Group defines where the script will be put, see all groups in the Scripts Window's header, menu "Scripts";
Submenu adds optional submenus for further control;
Tooltip is the (short) tooltip string for the menu entry.

Submenu lines are not required, use them if you want to provide extra options. To see which submenu the user chose, check the "__script__" dictionary in your code: __script__['arg'] has the defined keyword (the word after the submenu string name: all, sel or gui in the example above) of the chosen submenu. For example, if the user clicked on submenu 'Selected' above, __script__['arg'] will be "sel".

If your script requires extra data or configuration files, there is a special folder where they can be saved: see 'datadir' in Blender.Get.

Interaction with users:

Scripts can:

simply run and exit;
grab the main input event queue and process (or pass to Blender) selected keyboard, mouse, redraw events;
pop messages, menus and small number and text input boxes;
draw graphical user interfaces (guis) with OpenGL calls and native program buttons, which stay there accepting user input like any other Blender window until the user closes them;
make changes to the 3D View (set visible layer(s), view point, etc);
use external Python libraries, if available.

You can read the documentation for the Window, Draw and BGL modules for more information and also check Python's site for external modules that might be useful to you. Note though that any imported module will become a requirement of your script, since Blender itself does not bundle external modules.

Command line mode:

Python was embedded in Blender, so to access bpython modules you need to run scripts from the program itself: you can't import the Blender module into an external Python interpreter. But with "OnLoad" script links, the "-b" background mode and additions like the "-P" command line switch, Blender.Save, Blender.Load, Blender.Quit and the Library module, for many tasks it's possible to control Blender via some automated process using scripts.

Demo mode:

Blender has a demo mode, where once started it can work without user intervention, "showing itself off". Demos can render stills and animations, play rendered or real-time animations, calculate radiosity simulations and do many other nifty things. If you want to turn a .blend file into a demo, write a script to run the show and link it as a scene "OnLoad" scriptlink. The demo will then be played automatically whenever this .blend file is opened, unless Blender was started with the "-y" parameter.

The Game Engine API:

Blender has a game engine for users to create and play 3d games. This engine lets programmers add scripts to improve game AI, control, etc, making more complex interaction and tricks possible. The game engine API is separate from the Blender Python API this document references and you can find its own ref doc in the docs section of the main sites below.

Blender Data Structures:

Programs manipulate data structures. Blender python scripts are no exception. Blender uses an Object Oriented architecture. The bpython interface tries to present Blender objects and their attributes in the same way you see them through the User Interface ( the GUI ). One key to bpython programming is understanding the information presented in Blender's OOPS window where Blender objects and their relationships are displayed.

Each Blender graphic element ( Mesh, Lamp, Curve, etc.) is composed from two parts: An Object and ObData. The Object holds information about the position, rotation and size of the element. This is information that all elements have in common. The ObData holds information specific to that particular type of element.

Each Object has a link to its associated ObData. A single ObData may be shared by many Objects. A graphic element also has a link to a list of Materials. By default, this list is associated with the ObData.

All Blender objects have a unique name. However, the name is qualified by the type of the object. This means you can have a Lamp Object called Lamp.001 ( OB:Lamp.001 ) and a Lamp ObData called Lamp.001 ( LA:Lamp.001 )

For a more in-depth look at Blender internals, and some understanding of why Blender works the way it does, see the Blender Architecture document.

A note to newbie script writers:

Interpreted languages are known to be much slower than compiled code, but for many applications the difference is negligible or acceptable. Also, with profiling to identify slow areas and well thought optimizations, the speed can be considerably improved in many cases. Try some of the best bpython scripts to get an idea of what can be done, you may be surprised.

Version: 2.34

Author: The Blender Python Team

Note: this documentation was generated by epydoc, which can output html and pdf. For pdf it requires a working LaTeX environment.

Requires: Blender 2.34 or newer.

See Also:: www.blender3d.org: main site, www.blender.org: documentation and forum, www.elysiun.com: user forum, projects.blender.org, blender architecture: blender architecture document, www.python.org, www.python.org/doc

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