Creating a Qt for Python Application with Qt Quick

First, create a Qt for Python application project. Then, edit the boilerplate code to develop a small application that uses Qt Quick to display the text Hello World in several languages.

{A small Qt Quick application}

Creating an Empty Project

To create a Qt for Python application that has a main QML file:

  1. Select File > New Project > Application (Qt for Python) > Qt Quick Application - Empty > Choose.

    The Project Location dialog opens.

    {Project Location dialog}

  2. In Name, enter the project name. For example, hello_world_quick.
  3. In Create in, enter the path for the project files. For example, C:\Qt\examples.
  4. Select Next (on Windows and Linux) or Continue (on macOS) to open the Define Project Details dialog.

    {Define Project Details dialog}

  5. In PySide version, select the PySide version of the generated code.
  6. In Interpreter, select the Python interpreter to use for the project.
  7. Select the Create new virtual environment check box to use a clean Python environment that is independent of your global Python installation.
  8. In Path to virtual environment, specify the directory where to create the environment.
  9. Select Next or Continue.
  10. Review the project settings, and select Finish (on Windows and Linux) or Done (on macOS) to create the project.

The wizard generates the following files:

  • hello_world_quick.pyproject, which lists the files in the Python project.
  • main.py, which has some boilerplate code.
  • main.qml, which imports Qt Quick controls.

Adding Qt Quick Imports

The wizard adds the following imports to the main.py source file for access to QGuiApplication and QQmlApplicationEngine:

import sys
from pathlib import Path

from PySide6.QtGui import QGuiApplication
from PySide6.QtQml import QQmlApplicationEngine

Adding a Main Function

The wizard also adds a main function, where it creates a QGuiApplication instance and passes system arguments to the QGuiApplication object:

if __name__ == "__main__":
    app = QGuiApplication(sys.argv)
    ...

Loading the QML File

The following lines in the main class create a QQmlApplicationEngine instance and load the generated QML file to the engine object:

...
engine = QQmlApplicationEngine()
qml_file = Path(__file__).resolve().parent / "main.qml"
engine.load(qml_file)
...

Finally, the wizard adds code that checks whether the file was successfully loaded. If loading the file fails, the application exits with an error code. If loading succeeds, the wizard calls the app.exec() method to enter the Qt main loop and start executing the Qt code:

...
if not engine.rootObjects():
    sys.exit(-1)
sys.exit(app.exec())
...

Designing the UI

Open the main.qml file in the Edit mode to design a Qt Quick UI.

Adding Imports

Add imports for Qt Quick Controls and Layouts:

import QtQuick
import QtQuick.Window
import QtQuick.Controls
import QtQuick.Layouts

Adding Properties and Functions

The wizard adds a main window:

Window {
    width: 640
    height: 480
    visible: true
    title: qsTr("Hello World")
}

Add a property and function to randomly select the language of the displayed text:

    ...
    readonly property list<string> texts: ["Hallo Welt", "Hei maailma",
                                       "Hola Mundo", "Привет мир"]

function setText() {
    var i = Math.round(Math.random() * 3)
    text.text = texts[i]
}

Adding Qt Quick Controls

Add Text and Button QML types within a ColumnLayout type to design the UI:

    ColumnLayout {
    anchors.fill:  parent

    Text {
        id: text
        text: "Hello World"
        Layout.alignment: Qt.AlignHCenter
    }
    Button {
        text: "Click me"
        Layout.alignment: Qt.AlignHCenter
        onClicked:  setText()
    }
}

You can also use Qt Design Studio to design Qt Quick UIs.

Running the Application

Select the button to run the application.

See also Creating a Qt for Python Application with Qt Widgets and Develop Qt for Python Applications.

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