Question

All in the question title, and my simplified code below.
According to the docs:
http://www.riverbankcomputing.co.uk/static/Docs/PyQt4/html/qdialog.html#done
on clicking Ok, it should close and indeed if I close it using the window close button, it fires the event:

from PyQt4.QtGui import *
from PyQt4.QtCore import *

class MyDialog(QDialog):    
    def __init__(self):
        QDialog.__init__(self)
        self.button_box = QDialogButtonBox(self)
        self.button_box.addButton(self.button_box.Ok)
        self.connect(self.button_box, SIGNAL('accepted()'), self.on_accept)
        layout = QVBoxLayout()
        layout.addWidget(self.button_box)
        #self.setAttribute(Qt.WA_DeleteOnClose)
        self.setLayout(layout)
        self.connect(self.button_box, SIGNAL('destroyed(QObject*)'), self.on_destroyed)

    def on_destroyed(self, *args):
        print("destroying dialog")

    def on_accept(self):
        print("accepting")
        self.done(1)

    def closeEvent(self, event):
        print("close")
        return QDialog.closeEvent(self, event)

#    def __del__(self):
#        QDialog.destroy(self)

my_app = QApplication([])
my_widget = MyDialog()
result = my_widget.exec_()
del my_widget
#my_widget.destroy()
if result == 1:
    print("result!")
else:
    print("other result:", result)
my_app.exec_()

Answer 1

The answer came from http://www.riverbankcomputing.com/pipermail/pyqt/2011-April/029589.html
with many thanks to Hans-Peter Jansen

1. Don’t hook handler for destroyed signal onto the object being destroyed.(seems obvious in retrospect)

2. QDialog.accept() does not fire closeEvent, even though it does get destroyed – bug or documentation is misleading IMHO