PySide6 script that shows an empty window

Template

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# A script script that just displays
# an empty Qt6 window

import sys
from PySide6.QtWidgets import QApplication, QWidget


# 1 - Create a class inherited from QWidget

class Window(QWidget):

    def __init__(self):

        # If you don't init the superclass 
        # you get a run-time error
        super().__init__()
    

if __name__ == '__main__':
    
    # 2 - Create an instance of the QApplication class
    #     Make sure there isn't one already running.
    
    if not QApplication.instance():
        app = QApplication(sys.argv)
    else:
        app = QApplication.instance()

    # 3 - Create an instance of the Window class
    #     and show() it
    
    main_window = Window()
    main_window.show()
    
    # 4 - Start receiving events
    
    sys.exit(app.exec())

This is a simple template script I use so I don’t have to remember the boilerplate code each time I want to use PySide6. The only thing it does is display an empty Qt window but it has all the elements of a Qt/PySide application nonetheless, So here’s the breakdown:

After the necessary imports

  1. Create a Python class that is a QWidget subclass. QWidget is the base class of all Qt widget classes so you could use QPushButton or QDialog here instead. For more involved application that have toolbars, menubars etc you would use QMainWindow that provides them out of the box. In your class’ __init__() you have to __init__() the superclass (ie. QWidget) or you get a runtime error.

In the main script code

  1. Create a QApplication instance. This should be the first thing you do in your application/script. For non Qt Widget GUI application there is QGuiApplication and for terminal/console applications there is QCoreApplication. QApplication is singleton so if you try to create it twice you get RuntimeError: Please destroy the QApplication singleton before creating a new QApplication instance. (From now on I won’t be checking if the QApplication instance exists as all the examples are quite simple but it’s something to be aware of)

  2. Create an object of your class (in the script Window) and .show() it. (QWidget.show(), well, shows it on the screen.)

  3. Use QApplication.exec() to start the application event loop. With this your application’s main windows is displayed on your screen and is able to process events. When you exit the application, for instance by pressing the window’s close button app.exec() returns and your application exits. That’s about it.