[IPython-User] simple iPython example raises exception on sys.exit()

Dave T dave@davestechshop....
Tue Jun 5 10:29:22 CDT 2012

On Tue, Jun 5, 2012 at 9:57 AM, Matthias BUSSONNIER <
bussonniermatthias@gmail.com> wrote:

> Hi,
> Le 4 juin 2012 à 23:24, Dave a écrit :
> When I close the window of the running demo application, I see this error:
> An exception has occurred, use %tb to see the full traceback.
> SystemExit: 0
> Just don't use sys.exit(0) as you are not exiting python, but still
> running IPython.
> Add it if you wish to run your app from a (real) command line and have a
> return status.
> If I try to execute my code again, I get this:
> RuntimeError: A QApplication instance already exists.
> This is a PySide Bug that they "won't fix" as they don't consider it a
> bug.
> (see https://github.com/ipython/ipython/issues/1124)
> QApplication can only have one instance and quitting an app is apparently
> not considered a resin sufficient enough do delete the object...
> You can use this code from above issues :
> ...
> app=QtGui.QApplication.instance() # checks if QApplication already exists
> if not app: # create QApplication if it doesnt exist app =
> QtGui.QApplication(sys.argv)
> ….
> to reuse the application instance, it might have a few side effect, (not
> sure) but you shouldn't be confronted to it if you are starting with qt.

Matthias, thank you. That gave me a sufficient work around. Now I can work
more efficiently while I keep learning.
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