GTK+ debugging and development tool Parasite is a debugging and development tool that runs inside your GTK+ application's process. It can inspect your application, giving you detailed information on your UI, such as the hierarchy, X window IDs, widget properties, and more. You can modify properties on the fly in order to experiment with the look of your UI. But you can go further than that. You can actually modify your application logic while the program is running! Parasite includes an embedded Python shell that lets you write new code that directly interacts with your application's UI, regardless of the language the application is written in. Create new dialogs, attach temporary signal handlers to buttons, test out new logic, and gather additional debug information. Run it with "GTK_MODULES=gtkparasite $PROGRAM" to have it loaded with $PROGRAM.