Transitioning from Xlua to XPPython3

Laminar provides a Xlua plugin which is commonly used with Aircraft plugins. It is simple, but limited in functionality. If you’re familiar with Xlua and want to transition to python, here are some tools to make it easier for you.

Overview

Because nearly all Xlua plugins are for aircraft, we’ll describe XPPython3 in the context of using it as an aircraft plugin.

Installation

As with any XPPython3 plugin, the user must install XPPython3, once only, under Resources/plugins as described in Plugin Installation. That plugin will be responsible for loading all python-based plugins whether they be global, aircraft, or scenery plugins. (See also Global, Aircraft, and Scenery Plugins)

An aircraft-specific plugin will be installed under the Aircraft’s folder, under a new directory called plugins/PythonPlugins. This is analogous to xlua plugins being placed under plugins/xlua. The actual name of the main python plugin file must start with PI_, but otherwise does not matter:

<X-Plane>/
└─── Resources/
|    └─── plugins/
|         └─── XPPython3/     <--- standard XPPython3 installation
|         └─── PythonPlugins/ <--- folder for global python plugins
└─── Aircraft/
     └─── Cessna 172SP/
          └─── plugins/
               ├─── xlua/            <--- standard xlua plugins
               |    └─── ...
               └─── PythonPlugins/   <--- folder for python aircraft plugins
                    ├─── PI_MyPlugin.py
                    └─── PI_MyOtherPlugin.py

Placing your python plugin under your Aircraft folder means it will be loaded only when your aircraft is loaded, and unloaded when the user changes aircraft. Placing your plugin under the Resources/plugins global location would load your plugin for every flight.

How it works

Fundamentally, an aircraft plugin is nearly identical to any other plugin. It will likely read / write datarefs, set timers for delayed operation and respond to user and sim events.

The X-Plane SDK supports all of these actions of course, but as it’s designed for a C/C++ programmer it has not been simplified for typical use of an aircraft.

With XPPython3, we include a module (easy_python) that, together with some addition tools, mimics the Xlua interface. It provides the same functionality, and does the heavy lifting to convert this simplified interface back into native X-Plane API.

This means you can do simple-things simply, yet still have the full power of the SDK API (and XPPython3) if/when you want it.

The easiest way to see this is by examining a Typical Aircraft xlua Plugin.