Using PyQt in PyQGIS inside QGIS 3.16

Question

This code Using PyQt5 extracted from http://www.tutorialspoint.com does not work when I add it in a script in the console of QGIS 3.16. Can you enlighten me on this subject?

import sys
from PyQt5 import QtGui

def window():
    app = QtGui.QApplication(sys.argv)
    w = QtGui.QWidget()
    b = QtGui.QLabel(w)
    b.setText("Hello World!")
    w.setGeometry(100,100,200,50)
    b.move(50,20)
    w.setWindowTitle("PyQt")
    w.show()
    sys.exit(app.exec_())
    
    if __name__ == '__main__':
       window()

Answer 1

I think the original code have a different indentation :

import sys
from PyQt5 import QtWidgets

def window():
    app = QtWidgets.QApplication(sys.argv)
    w = QtWidgets.QWidget()
    b = QtWidgets.QLabel(w)
    b.setText("Hello World!")
    w.setGeometry(100,100,200,50)
    b.move(50,20)
    w.setWindowTitle("PyQt")
    w.show()
    sys.exit(app.exec_())


if __name__ == '__main__':
    window()

It's a code to create a widget with a label Hello World! inside a QApplication app loop.

But, when you launch QGIS, it's already a Qt application with its own loop. So, the working code will be :

import sys
from PyQt5 import QtWidgets

def window():
    w = QtWidgets.QWidget()
    b = QtWidgets.QLabel(w)
    b.setText("Hello World!")
    w.setGeometry(100,100,200,50)
    b.move(50,20)
    w.setWindowTitle("PyQt")
    return w


w = window()
w.show()