Using a Designer UI File in Your Qt for Python Application

To demonstrate, we use the Qt Widgets animation easing example.

The application consists of one source file, easing.py, a UI file form.ui, a resource file easing.qrc and the project file, easing.pyproject file in the YAML format:

{
    "files": ["easing.qrc", "ui_form.py", "easing.py", "easing_rc.py",
              "form.ui"]
}

The UI file is converted to Python code building the form using the User Interface Compiler (uic):

uic -g python form.ui > ui_form.py

Since the top level widget is named Form, this results in a Python class named Ui_Form being generated. It provides a function setupUi(), taking the widget as parameter, which is called to create the UI elements:

from ui_form import Ui_Form
...
class Window(QtWidgets.QWidget):
    def __init__(self, parent=None):
        super(Window, self).__init__(parent)

        self.m_ui = Ui_Form()
        self.m_ui.setupUi(self)

Later on, the widgets can be accessed via the Ui_Form class:

self.m_ui.graphicsView.setScene(self.m_scene)

Besides setupUi(), Ui_Form provides another method retranslateUi(), which can be called in reaction to a QEvent of type QEvent.LanguageChange, which indicates a change in the application language.

The UiTools Approach▲

from PySide2.QtUiTools import QUiLoader

if __name__ == '__main__':
    # Some code to obtain the form file name, ui_file_name
    app = QApplication(sys.argv)
    ui_file = QFile(ui_file_name)
    if not ui_file.open(QIODevice.ReadOnly):
        print("Cannot open {}: {}".format(ui_file_name, ui_file.errorString()))
        sys.exit(-1)
    loader = QUiLoader()
    widget = loader.load(ui_file, None)
    ui_file.close()
    if not widget:
        print(loader.errorString())
        sys.exit(-1)
    widget.show()
    sys.exit(app.exec_())