QML Application Tutorial

This tutorial provides a quick walk-through of a python application that loads a QML file. QML is a declarative language that lets you design UIs faster than a traditional language, such as C++. The QtQml and QtQuick modules provides the necessary infrastructure for QML-based UIs.

In this tutorial, you’ll also learn how to provide data from Python as a QML initial property, which is then consumed by the ListView defined in the QML file.

Before you begin, install the following prerequisites:

The following step-by-step instructions guide you through application development process using Qt Creator:

  1. Open Qt Creator and select File > New File or Project.. menu item to open following dialog:

    ../../_images/newpyproject.png

  2. Select Qt for Python - Empty from the list of application templates and select Choose.

    ../../_images/pyprojname.png

  3. Give a Name to your project, choose its location in the filesystem, and select Finish to create an empty main.py and main.pyproject.

    ../../_images/pyprojxplor.png

    This should create a main.py and `main.pyproject files for the project.

  4. Download Main.qml, qmldir and logo.png and place them in a subdirectory named App in your project folder. This creates a basic QML module.

  5. Double-click on main.pyproject to open it in edit mode, and append view.qml and logo.png to the files list. This is how your project file should look after this change:

    {
    "files": ["main.py", "App/Main.qml", "App/logo.png", "App/qmldir"]
}

  6. Now that you have the necessary bits for the application, import the Python modules in your main.py, and download country data and format it:

     1import sys
 2import urllib.request
 3import json
 4
 5from PySide6.QtQuick import QQuickView
 6from PySide6.QtCore import QStringListModel
 7from PySide6.QtGui import QGuiApplication
 8
 9
10if __name__ == '__main__':
11
12    # get our data
13    url = "http://country.io/names.json"
14    response = urllib.request.urlopen(url)
15    data = json.loads(response.read().decode('utf-8'))
16
17    # Format and sort the data
18    data_list = list(data.values())
19    data_list.sort()

  7. Now, set up the application window using PySide6.QtGui.QGuiApplication, which manages the application-wide settings.

     1import sys
 2import urllib.request
 3import json
 4
 5from PySide6.QtQuick import QQuickView
 6from PySide6.QtCore import QStringListModel
 7from PySide6.QtGui import QGuiApplication
 8
 9
10if __name__ == '__main__':
11
12    # get our data
13    url = "http://country.io/names.json"
14    response = urllib.request.urlopen(url)
15    data = json.loads(response.read().decode('utf-8'))
16
17    # Format and sort the data
18    data_list = list(data.values())
19    data_list.sort()
20
21    # Set up the application window
22    app = QGuiApplication(sys.argv)
23    view = QQuickView()
24    view.setResizeMode(QQuickView.SizeRootObjectToView)

    Note

    Setting the resize policy is important if you want the root item to resize itself to fit the window or vice-a-versa. Otherwise, the root item will retain its original size on resizing the window.

  8. You can now expose the data_list variable as a QML initial property, which will be consumed by the QML ListView item in view.qml.

     1import sys
 2import urllib.request
 3import json
 4
 5from PySide6.QtQuick import QQuickView
 6from PySide6.QtCore import QStringListModel
 7from PySide6.QtGui import QGuiApplication
 8
 9
10if __name__ == '__main__':
11
12    # get our data
13    url = "http://country.io/names.json"
14    response = urllib.request.urlopen(url)
15    data = json.loads(response.read().decode('utf-8'))
16
17    # Format and sort the data
18    data_list = list(data.values())
19    data_list.sort()
20
21    # Set up the application window
22    app = QGuiApplication(sys.argv)
23    view = QQuickView()
24    view.setResizeMode(QQuickView.SizeRootObjectToView)
25
26    # Expose the list to the Qml code
27    my_model = QStringListModel()
28    my_model.setStringList(data_list)
29    view.setInitialProperties({"myModel": my_model})

  9. Load the Main.qml to the QQuickView and call show() to display the application window.

     1import sys
 2import urllib.request
 3import json
 4
 5from PySide6.QtQuick import QQuickView
 6from PySide6.QtCore import QStringListModel
 7from PySide6.QtGui import QGuiApplication
 8
 9
10if __name__ == '__main__':
11
12    # get our data
13    url = "http://country.io/names.json"
14    response = urllib.request.urlopen(url)
15    data = json.loads(response.read().decode('utf-8'))
16
17    # Format and sort the data
18    data_list = list(data.values())
19    data_list.sort()
20
21    # Set up the application window
22    app = QGuiApplication(sys.argv)
23    view = QQuickView()
24    view.setResizeMode(QQuickView.SizeRootObjectToView)
25
26    # Expose the list to the Qml code
27    my_model = QStringListModel()
28    my_model.setStringList(data_list)
29    view.setInitialProperties({"myModel": my_model})
30
31    # Load the QML file
32    # Add the current directory to the import paths and load the main module.
33    view.engine().addImportPath(sys.path[0])
34    view.loadFromModule("App", "Main")
35
36    # Show the window
37    if view.status() == QQuickView.Error:
38        sys.exit(-1)
39    view.show()

  10. Finally, execute the application to start the event loop and clean up.

     1import sys
 2import urllib.request
 3import json
 4
 5from PySide6.QtQuick import QQuickView
 6from PySide6.QtCore import QStringListModel
 7from PySide6.QtGui import QGuiApplication
 8
 9
10if __name__ == '__main__':
11
12    # get our data
13    url = "http://country.io/names.json"
14    response = urllib.request.urlopen(url)
15    data = json.loads(response.read().decode('utf-8'))
16
17    # Format and sort the data
18    data_list = list(data.values())
19    data_list.sort()
20
21    # Set up the application window
22    app = QGuiApplication(sys.argv)
23    view = QQuickView()
24    view.setResizeMode(QQuickView.SizeRootObjectToView)
25
26    # Expose the list to the Qml code
27    my_model = QStringListModel()
28    my_model.setStringList(data_list)
29    view.setInitialProperties({"myModel": my_model})
30
31    # Load the QML file
32    # Add the current directory to the import paths and load the main module.
33    view.engine().addImportPath(sys.path[0])
34    view.loadFromModule("App", "Main")
35
36    # Show the window
37    if view.status() == QQuickView.Error:
38        sys.exit(-1)
39    view.show()
40
41    # execute and cleanup
42    app.exec()
43    del view

  11. Your application is ready to be run now. Select Projects mode to choose the Python version to run it.

    ../../_images/projectsmode.png

Run the application by using the CTRL+R keyboard shortcut to see if it looks like this:

../../_images/qmlapplication.png

You could also watch the following video tutorial for guidance to develop this application: