[IPython-dev] ipython slowdown with qt

Eric Firing efiring at hawaii.edu
Fri Aug 15 16:22:12 EDT 2014

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.]


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:

%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.

%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.


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