dialog.py

from gi.repository import Gtk

def alert(message):
    dialog = Gtk.MessageDialog(None, Gtk.MessageType.INFO, message_format=message)
    dialog.set_border_width(10)
    #dialog.add_button("Cancel", Gtk.ResponseType.CANCEL)
    dialog.add_button("OK", Gtk.ResponseType.OK)
    dialog.run()
    dialog.destroy()

def confirm(question):
    dialog = Gtk.MessageDialog(None, Gtk.MessageType.INFO, message_format=question)
    dialog.set_border_width(10)
    dialog.add_button("Cancel", Gtk.ResponseType.CANCEL)
    dialog.add_button("OK", Gtk.ResponseType.OK)
    response = dialog.run()
    dialog.destroy()
    if response == -5:
        return True
    return False

if __name__ == '__main__':
    alert('This is a simple alert')
    if confirm('Do you want to quit?'):
        print 'bye'