Plugin Development

To develop python3 plugins, you’ll need to have the XPPython3 plugin installed first (and python3, of course).

Output from python print() statements, python coding errors and exceptions will appear in XPPython3Log.txt.

Note

Errors in some calls to XP interface don’t cause exceptions but rather just terminate the plugin’s method (e.g., terminate the flightloop) with no further message. These are hard to debug, but adding print statements to you plugin to verify statement execution will help.

If you write bad python code, or use Python2 rather than Python3 syntax, you’ll see the exception in XPPython3Log.txt.

Documentation

You will find these resources helpful:

  • Modules Documentation

    Note we use a Simplified Python Interface in module xp. You’ll find it much faster and easier to write new code using this interface and won’t wear out your XPLM keys. You can use the older style (e.g., import XPLMMenus, but new code will work better with the xp style interface.)

    We’ve attempted to fully document the API here, noting changes from the official C-Language SDK. (Don’t forget to use the Search field in the header of each of these documentation web pages to find what you’re looking for!)

    Most of the APIs in this documentation include example source code which can be cut and pasted into the Mini Python Interpreter.

  • Change Log. Lists recent changes to this SDK.

  • Python Packages and Importing. Information about python packages and proper way to import.

  • Using imgui. Using Dear IMGUI (and OpenGL) with XPPython3.

  • Global, Aircraft, and Scenery Plugins: Though most plugins are Global Plugins, you can code Aircraft and Scenery plugins.

And for something completely different:

Code Examples

  • Quick Start. Bare-bones skeleton and Hello World to get you started.

  • Samples and Demos. Ported versions of C++ and Python2 demos. Many of these are copied to your PythonPlugins/samples/ folder on installation, but there may be more, and more recent demos on github. You can download the latest set, refreshing the samples folder, by selecting Download Samples from the XPPython3 menu.

  • XPython/examples/ (github) Python test code exercising each interface is in this directory, organized primarily one example file per module. You can copy them into your /PythonPlugins directory to have them executed by X-Plane with few modifications.

    Most of these examples where used to exercise specific aspects of the API rather than provide useful, instructive examples. See Samples and Demos if you’re looking for something more helpful.

Tools

  • Mini Debugger (See Mini Python Interpreter.)

    The PI_MiniPython.py plugin, available under PythonPlugins/samples/, allows you to type in python expressions in a running application and see the results: You’ll need to move it from samples up into the PythonPlugins directory in order for it to load.

  • Plugin Performance (See Plugin Performance.)

    XPPython3 monitors the performance of individual python plugins and displays this information when you select the XPPython3 -> Performance menu item.

  • Python Stubs (Download from github: stubs.zip.)

    Because the XPLM* modules are contained within a shared library, they are not useful for support tools such as pylint. For this reason, we’ve included a set of stubs. See XPPython3 Stubs for details.

    Note

    Do not place stubs in XPPython3 or PythonPlugins folder where they will be found by X-Plane! The stubs do not actually execute code.

  • Debug Config Initialization (See Preferences File.)

    For debugging, we’ve added some run-time flags which can be configured and stored. These increase the level of internal debugging output, and increase the frequency of buffer flushing. Will slow down execution time a small bit, but may make your debugging easier.

Advanced Topics

  • Porting from older plugin?

    Note that XPPython3 is backward compatible to the API, but you will need to make changes to support python3 vs. python2. That being said XPPython3 has a new simplified API which (though not backward compatible) will make new code easier to write.

    • Changes from Python2 SDK

    • Porting Notes

    • NOAA Weather Plugin

      Unofficial port of Joan’s NOAWeather plugin. Use git-compare to see what types of things change from python2 to python3. (Joan is familiar with the changes and will be responsible for official support in the future – this is merely a porting example.)

  • Using python multiprocessing or subprocess? See Multiprocessing and XPPython3 for hints and an example.

All Advanced topcs