Writing a Thunarx-Python extension is a fairly straight-forward process. One simply imports the thunarx module and creates a class which is derived from a number of the thunarx module's classes. When an extension derives a class, it becomes a "provider", telling Thunarx to ask it for information. There are several types of providers available for extensions to use: there is MenuProvider, PropertyPageProvider, RenamerProvider, and PreferencePageProvider, all of which will be explained in more detail below. Your class can be derived from multiple providers.
Here are the basic steps:
1. A script is written and installed to the standard python extensions install path
2. Thunar is (re)started and loads the Thunarx-Python C extension, which in turn loads all python extensions
3. Any python script in the standard python extensions install path that imports the thunarx module and derives the main class from a thunarx module class will be loaded
The system-wide install path is $PREFIX/lib/thunarx-2/python (or thunarx-1). However, some 64 bit distributions, such as Fedora, put Thunarx-Python extensions in $PREFIX/lib64/thunarx-1/python (or thunarx-1).