How does an empty list work to initialize a QApplication object?

I'm new to python and PyQt. When I studyting how to code with PyQt5, I see many people initialize the QApplication object in such way:

app = QtWidgets.QApplication([])

It's legal, but how do I realize it?

I guess that its because the paraments of QApplication() is like (argc, **argv), so an empty list is useful to make a default initialization. But I dont really know how the class works. May I just use QtWidgets.QApplication(sys.argv) to avoid any trouble?

Solution

QAplication takes a list as a positional argument, so it won't work without it. That list can contain additional instructions like [-style, fusion], but QApplication will run fine without additional instructions (empty list).

The 'proper' way to initialise QApplication is:

app = QApplication(sys.argv)

That way any arguments that were used to start the program are passed on to QApplication.

The empty list you're seeing is probably from people providing a Minimal, Reproducible Example. When the problem at hand doesn't have anything to do with arguments for QApplication, you can just use an empty list.