#!/usr/bin/env python3

import gi
gi.require_version("Gtk", "3.0")
from gi.repository import Gtk

class MyWindow(Gtk.Window):

    def __init__(self):
        Gtk.Window.__init__(self, title = "Hello World!")

        self.box = Gtk.Box(spacing = 6)
        self.add(self.box)

        self.button1 = Gtk.Button(label = "Hello")
        self.button1.connect("clicked", self.on_button1_clicked)
        self.box.pack_start(self.button1, True, True, 0)

        self.button2 = Gtk.Button(label = "Goodbye")
        self.button2.connect("clicked", self.on_button2_clicked)
        self.box.pack_start(self.button2, True, True, 0)

    def on_button1_clicked(self, widget):
        print("Hello!")

    def on_button2_clicked(self, widget):
        print("Goodbye!")
        Gtk.main_quit()

window = MyWindow()
window.connect("delete-event", Gtk.main_quit)
window.show_all()

Gtk.main()