hwd.actionEnglish.triggered.connect( lambda: set_menu_langugage_english(hwd)) hwd.actionJapanese.triggered.connect( lambda: set_menu_langugage_japanese(hwd)) hwd.actionAbout.triggered.connect(about) class MyDialog(QtWidgets.QMainWindow): def __init__(self): super(MyDialog, self).__init__() self.ffmpeg = None def closeEvent(self, evnt): super(MyDialog, self).closeEvent(evnt) if __name__ == "__main__": import sys app = QtWidgets.QApplication(sys.argv) MainWindow = MyDialog() #MainWindow.setUnifiedTitleAndToolBarOnMac(True) ui = Ui_MainWindow() ui.setupUi(MainWindow) ui.app = app ui.win = MainWindow set_up_actions(ui) MainWindow.show() sys.exit(app.exec_())