Internationalization (translation) of dialog and the main window in a pyqt5 application

Question

I am trying to translate my small application written in pyside2/pyqt5 to several languages, for example, Chinese. After googling, I managed to change the main window to Chinese

Answer 1

You have to overwrite the changeEvent() method and call retranslateUi() when the event is of type QEvent::LanguageChange, on the other hand the QTranslator object must be a member of the class but it will be deleted and it will not exist when the changeEvent() method is called.

Finally assuming that the Language menu is used to establish only translations, a possible option is to establish the name of the .qm as data of the QActions and to use the triggered method of the QMenu as I show below:

from PySide2 import QtCore, QtGui, QtWidgets
from mainui import Ui_MainWindow

from dialogui import Ui_Dialog

class OptionsDialog(QtWidgets.QDialog,Ui_Dialog):
    def __init__(self,parent):
        super().__init__(parent)
        self.setupUi(self)

    def changeEvent(self, event):
        if event.type() == QtCore.QEvent.LanguageChange:
            self.retranslateUi(self)
        super(OptionsDialog, self).changeEvent(event)

class MainWindow(QtWidgets.QMainWindow,Ui_MainWindow):
    def __init__(self):
        super().__init__()
        self.setupUi(self)
        self.m_translator = QtCore.QTranslator(self)
        self.actionConfigure.triggered.connect(self.showdialog)
        self.menuLanguage.triggered.connect(self.change_lang)
        # set translation for each submenu
        self.actionChinese.setData('zh_CN')

    @QtCore.Slot()
    def showdialog(self):
        dlg = OptionsDialog(self)
        dlg.exec_()

    @QtCore.Slot(QtWidgets.QAction)
    def change_lang(self, action):
        QtCore.QCoreApplication.instance().removeTranslator(self.m_translator)
        if self.m_translator.load(action.data()):
            QtCore.QCoreApplication.instance().installTranslator(self.m_translator)

    def changeEvent(self, event):
        if event.type() == QtCore.QEvent.LanguageChange:
            self.retranslateUi(self)
        super(MainWindow, self).changeEvent(event)

if __name__=='__main__':
    import sys
    app = QtWidgets.QApplication(sys.argv)
    mainWin = MainWindow()
    mainWin.show()
    ret = app.exec_()
    sys.exit(ret)