linguist

(You can also check this code in the repository)

from pathlib import Path
import sys

from PySide6.QtCore import (QItemSelection, QLibraryInfo, QLocale, QTranslator,
                            Qt, Slot)
from PySide6.QtWidgets import (QAbstractItemView, QApplication, QListWidget,
                               QMainWindow, QWidget)


import linguist_rc


class Window(QMainWindow):
    def __init__(self):
        super().__init__()
        file_menu = self.menuBar().addMenu(self.tr("&File"))
        quit_action = file_menu.addAction(self.tr("Quit"))
        quit_action.setShortcut(self.tr("CTRL+Q"))
        quit_action.triggered.connect(self.close)
        help_menu = self.menuBar().addMenu(self.tr("&Help"))
        about_qt_action = help_menu.addAction(self.tr("About Qt"))
        about_qt_action.triggered.connect(qApp.aboutQt)

        self._list_widget = QListWidget()
        self._list_widget.setSelectionMode(QAbstractItemView.MultiSelection)
        self._list_widget.selectionModel().selectionChanged.connect(self.selection_changed)
        self._list_widget.addItem("C++")
        self._list_widget.addItem("Java")
        self._list_widget.addItem("Python")
        self.setCentralWidget(self._list_widget)

    @Slot(QItemSelection, QItemSelection)
    def selection_changed(self, selected, deselected):
        count = len(self._list_widget.selectionModel().selectedRows())
        message = self.tr("%n language(s) selected", "", count)
        self.statusBar().showMessage(message)


if __name__ == '__main__':
    app = QApplication(sys.argv)

    path = QLibraryInfo.location(QLibraryInfo.TranslationsPath)
    translator = QTranslator(app)
    if translator.load(QLocale.system(), 'qtbase', '_', path):
        app.installTranslator(translator)
    translator = QTranslator(app)
    path = ':/translations'
    if translator.load(QLocale.system(), 'example', '_', path):
        app.installTranslator(translator)

    window = Window()
    window.show()
    sys.exit(app.exec())
<!DOCTYPE RCC><RCC version="1.0">
<qresource>
    <file>translations/example_de.qm</file>
</qresource>
</RCC>
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE TS>
<TS version="2.1" language="de_DE" sourcelanguage="de_DE">
<context>
    <name>Window</name>
    <message>
        <location filename="main.py" line="56"/>
        <source>&amp;File</source>
        <translation>&amp;Datei</translation>
    </message>
    <message>
        <location filename="main.py" line="57"/>
        <source>Quit</source>
        <translation>Beenden</translation>
    </message>
    <message>
        <location filename="main.py" line="58"/>
        <source>CTRL+Q</source>
        <translation>CTRL+B</translation>
    </message>
    <message>
        <location filename="main.py" line="60"/>
        <source>&amp;Help</source>
        <translation>Hilfe</translation>
    </message>
    <message>
        <location filename="main.py" line="61"/>
        <source>About Qt</source>
        <translation>Über Qt</translation>
    </message>
    <message numerus="yes">
        <location filename="main.py" line="75"/>
        <source>%n language(s) selected</source>
        <translation>
            <numerusform>Eine Sprache ausgewählt</numerusform>
            <numerusform>%n Sprachen ausgewählt</numerusform>
        </translation>
    </message>
</context>
</TS>