gio_dbus.py

bus = Gio.bus_get_sync(Gio.BusType.SYSTEM)
bus.signal_subscribe(None, 'org.freedesktop.login1.Manager',
                     'PrepareForSleep', None, None,
                     Gio.DBusSignalFlags.NONE,
                     on_prepare_for_sleep)


def on_prepare_for_sleep(connection, sender_name, object_path,
                         interface_name, signal_name, parameters,
                         *user_data):
    """Handle dbus prepare for sleep signal."""

    print('Called')