Hi,

I have a python project that works fine with PySide6 6.4.3 and below. But it doesn't work after the upgrade to the recent one PySide6 6.5.0. The problem is with a constructor of MainWindow that is inherited from 2 classes (QMainWindow and UI-class created by Qt Designer).

Here is the code to reproduce the problem:

from PySide6.QtWidgets import QApplication, QMainWindow, QLabel

class Ui_X_MainWindow(object):
    def setupUi(self, MainWindow):
        MainWindow.resize(400, 300)
        self.lbl = QLabel(self)

class MainWindow(QMainWindow, Ui_X_MainWindow):
    def __init__(self):
        QMainWindow.__init__(self, parent=None)
        self.setupUi(self)
        self.lbl.setText("XXX")

app = QApplication([])
window = MainWindow()
window.show()
app.exec()

Here is an error:

window = MainWindow()
             ^^^^^^^^^^^^^^^^^
File "main.py", line 11, in _init_
  QMainWindow._init_(self, parent=None)
TypeError: object._init_() takes exactly one argument (the instance to initialize)

I think this code is based on Qt-examples as I have it in my project for 2-3 years already. But eventually it doesn't work anymore with PySide6 6.5.0 and I don't understand is it a bug or I need to change something.

I've this problem confirmed on Windows but my users reported the same for Linux Ubuntu and MacOS. I see similar reports on stackoverflow.org for recent days.