Exceptions in PyQt event loop and ipython

Question

I have a PyQt program that is displaying some widgets and buttons.

I want the program to run either as a standalone python instance, or inside an ipython environment. I

Answer 1

Actually, the dev's answer pointed me in the right direction: the problem is that each time an ipython cell is executed, a new sys.excepthook is monkeypatched, once the execution is done, the sys.excepthook is brought back to the previous one (see ipkernel/kernelapp.py).

Because of this, changing sys.excepthook in a normal ipython cell instruction will not change the excepthook that is executed during the qt event loop.

A simple solution is to monkeypatch sys.excepthook inside a qt event:

from PyQt4 import QtCore, QtGui
import sys
from traceback import format_exception

def new_except_hook(etype, evalue, tb):
    QtGui.QMessageBox.information(None, 
                                  str('error'),
                                  ''.join(format_exception(etype, evalue, tb)))

def patch_excepthook():
    sys.excepthook = new_except_hook
TIMER = QtCore.QTimer()
TIMER.setSingleShot(True)
TIMER.timeout.connect(patch_excepthook)
TIMER.start()

A nice thing about this method is that it works for standalone and ipython execution alike.

I guess one could also imagine to monkey patch a different version of new_except_hook depending on what widget is triggering the exception by calling patch_excepthook inside the event_handler of each widget.