#!/usr/bin/python3

import sys
from gi.repository import Gtk


class PythonApp(Gtk.Application):

    def __init__(self):
        Gtk.Application.__init__(
            self, application_id="org.example.PythonGnome")

        self.connect("activate", self.on_activate)

    def on_activate(self, app):
        window = Gtk.ApplicationWindow(application=app)
        window.show_all()

app = PythonApp()
exit_status = app.run(None)
sys.exit(exit_status)