from gi.repository import Gtk

from gi.repository import Gdk

import sys

class MyWindow(Gtk.ApplicationWindow):

    # a window

    def __init__(self, app):

        Gtk.Window.__init__(self, title="Spinner Example", application=app)

        self.set_default_size(200, 200)

        self.set_border_width(30)

        # a spinner

        self.spinner = Gtk.Spinner()

        # that by default spins

        self.spinner.start()

        # add the spinner to the window

        self.add(self.spinner)

    # event handler

    # a signal from the keyboard (space) controls if the spinner stops/starts

    def do_key_press_event(self, event):

        # keyname is the symbolic name of the key value given by the event

        keyname = Gdk.keyval_name(event.keyval)

        # if it is "space"

        if keyname == "space":

            # and the spinner is active

            if self.spinner.get_property("active"):

                # stop the spinner

                self.spinner.stop()

            # if the spinner is not active

            else:

                # start it again

                self.spinner.start()

        # stop the signal emission

        return True

class MyApplication(Gtk.Application):

    def __init__(self):

        Gtk.Application.__init__(self)

    def do_activate(self):

        win = MyWindow(self)

        win.show_all()

    def do_startup(self):

        Gtk.Application.do_startup(self)

app = MyApplication()

exit_status = app.run(sys.argv)

sys.exit(exit_status)