[IPython-dev] ipython slowdown with qt

Jens Nielsen jenshnielsen at gmail.com
Fri Aug 15 17:05:14 EDT 2014

While I can reproduce the issue using %gui qt I can also reproduce it with
the WX backend (%qui wx) with more or less the same symptoms. However, I
don't see the issue with either of the 'tk' or the 'osx' backends. And yes
the issue is reproducible in a python installation without any mpl


On Fri, Aug 15, 2014 at 9:22 PM, Eric Firing <efiring at hawaii.edu> wrote:

> On 2014/08/15, 9:37 AM, Derek Homeier wrote:
> > When using MPL with ipython —pylab and the Quartz version of PyQT4,
> > the interpreter seems to be slow down extremely after running for a
> > little while. Weirdly this is not connected to any graphics display
> > and in fact happens even without any plotting window opened, i.e. the
> > ipython shell just randomly becomes completely unresponsive and hangs
> > for several seconds on simple tasks like typing or navigating through
> > history. The plotting itself actually does not appear to perform any
> > worse than it used to under Mountain Lion.
> [I'm switching the subject because my comments below relate to ipython
> and matplotlib, and are no longer Anaconda-specific.]
> Derek,
> Thanks.  A few days ago, when I switched from testing on linux to
> testing on osx, exactly this ipython slowdown was happening to me--but I
> lost track of what combination of versions and invocations was causing
> it.  Therefore I have been concentrating on the severe problem which
> was, for me, 100% repeatable, and involved macosx backend, not Qt.  I
> expect the macosx-relatec problem will go away after Ilan uploads the
> revised Anaconda ipython for python 3.
> Now I find I can repeat the ipython problem on Homebrew python 3
> (framework--with Quartz app) and Anaconda with the un-fixed ipython
> (which is running without starting a Quartz app):
> ipython --pylab=qt
> Leave it alone for a bit.  Try scrolling through history.  Long delay,
> even in responding to Ctrl-C.  Evidently key events are stacking up and
> not being processed.  Now try:
> ipython
> %pylab qt
> I see the slowdown with this, also.  The response delay seems to get
> worse with time. It renders the session unusable after only a few minutes.
> ipython
> %gui qt
> And I still see it, so this appears to be a problem in ipython's PyQt4
> gui handling, not directly related to matplotlib.  All on Mavericks,
> running ipython from Apple's terminal.
> Eric
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