Trac plugins are an excellent example of how to use entry points in Python. In order to function and be visible to Trac, the plugin must define a trac.plugins entry point that returns a list of all plugin components.
This functionality is implemented by the loader.py Trac module. Here is a simple illustration of what it does.
![](http://4.bp.blogspot.com/_qOKUA2GftVM/Saw_sbjoxlI/AAAAAAAAAGw/swQdJSQ1_4I/s320/trac_plugin_loading.png)
Here, the Trac loader retrieves a list of all Python eggs currently installed on the system. It will determine if the egg is a Trac plugin by examining the entry points provided by each egg. If it finds the trac.plugins entry point, all components of that plugin will be loaded.