Some exceptions are not shown in qtconsole

[ccordoba12]

The following code (preceded by a %gui qt) doesn't print a NameError exception in qtconsole every time fun is called. Instead it's printed in the terminal where it was started:

from PyQt4.QtCore import QTimer

def fun():
    print "there will be an exception after this"
    a

timer = QTimer()
timer.start(1000)
timer.timeout.connect(fun)

What is the reason for this?

[minrk]

I think PyQt registers its own except hook for exceptions raised in Qt callbacks.

[josselex]

But why are these exceptions then shown in the terminal and not in the console? (And can I route this somehow to the console?)

[minrk]

But why are these exceptions then shown in the terminal and not in the console?

Because it is the sys.excepthook registered by IPython that sends the traceback to the frontend. Since the IPython excepthook doesn't get called, the traceback is drawn to the terminal, which is the default behavior.

[josselex]

Ok. Now i'm trying to ouput the error to the frontend. But It does not work, when called from QT:

import IPython,sys,PyQt4
#%% function to print the last exception
def print_excep():
    print "print_excep"
    IPython.get_ipython().showtraceback()
#%% make an exception
a
#%% this works
print_excep()
#%% called "from Qt" this does not work
PyQt4.QtCore.QTimer.singleShot(1000,print_excep)

"print_excep" gets output on the console, but not the traceback

[josselex]

I do this because I want to do the following to get it work to print errors from qt:

def print_excep(etype,evalue,tb):
    print "print_excep"
    IPython.get_ipython().showtraceback()
#%% register an excepthook for qt. 
#%% I don't know why it only works when called from the qt event loop
def prepare_excepthook():
    sys.excepthook = print_excep    
PyQt4.QtCore.QTimer.singleShot(0,prepare_excepthook)
#%% produce an error from qt event loop
def error_in_func():
    a
PyQt4.QtCore.QTimer.singleShot(0,error_in_func)