Why do I need “sys.argv” to start a QApplication in PyQt?

Question

I try to understand what PyQt does. And one of the first things I didn't, was:

QApplication(sys.argv)

Why do I have to give QApplication this argument? I know what sys.argv does. But in my Scripts I wouldn't need it.

Answer 1

This calls the constructor of the C++ class QApplication. It uses sys.argv (argc and argv in C++) to initialize the QT application. There are a bunch of arguments that you can pass to QT, like styles, debugging stuff and so on.

Take a look at this for a full list of the options.

Answer 2

QApplication takes a list of strings as input.

So you can forward sys.argv or simply an empty list:

app = QApplication([])