import gi

gi.require_version('Gtk', '4.0')
from gi.repository import Gtk

# https://pygobject.gnome.org/tutorials/gtk4/layout-widgets.html

class MyWindow(Gtk.ApplicationWindow):
    def __init__(self, **kargs):
        super().__init__(**kargs, title='Hello World')

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

        button1 = Gtk.Button(label='Hello')
        button1.connect('clicked', self.on_button1_clicked)
        box.append(button1)

        button2 = Gtk.Button(label='Goodbye')
        button2.props.hexpand = True
        button2.connect('clicked', self.on_button2_clicked)
        box.append(button2)

    def on_button1_clicked(self, _widget):
        print('Hello')

    def on_button2_clicked(self, _widget):
        print('Goodbye')


def on_activate(app):
    # Create window
    win = MyWindow(application=app)
    win.present()


app = Gtk.Application(application_id='com.example.App')
app.connect('activate', on_activate)

app.run(None)