'To keep track of to the last focused widget'

def change_last_focused_widget(self, old, now):

    if ((now is None) and (QApplication.activeWindow() is not None)):
        QApplication.activeWindow().setFocus()
        self.last_focused_widget = QApplication.focusWidget()
    elif (now is not None):
        self.last_focused_widget = now
    self.previous_focused_widget = old
