This example shows how Qt's style mechanisms can be used to set a dark theme. It adapts the text editor from example 7.
As you can see in main.py, this example uses QApplication.setStyle(...) and a QPalette to change the application's colors:
# Force the style to be the same on all OSs:
app.setStyle("Fusion")
# Now use a palette to switch to dark colors:
palette = QPalette()
palette.setColor(QPalette.Window, QColor(53, 53, 53))
palette.setColor(QPalette.WindowText, Qt.white)
...
app.setPalette(palette)
The rest of the code is the same as for the original version of the text editor.
To run this example yourself, please follow the instructions in the README of this repository.