class Application:

    def __init__(self):
        self.callbacks = Callbacks()

        # Load our Glade interface configuration
        self.XML = gtk.glade.XML('somefile.glade')

        # Automatically connect all signals to callbacks
        self.XML.signal_autoconnect(self.callbacks)

class Callbacks:

    def on_windowMain_destroy(self, window):
        print 'Exiting by user request.'
        gtk.main_quit()