[PySide] QTimer reference leaks in pyside vs pyqt

Josh Pieper jjp at pobox.com
Sat Jun 14 03:41:29 CEST 2014

Philip Starkey wrote:
> Josh Pieper <jjp <at> pobox.com> writes:
> > Hello, I have an application that wants to repeatedly schedule
> > callbacks into the QT event loop.  With pyside, memory usage grows
> > over time, as python doesn't appear to be able to free things up.
> > objgraph shows a growing number of QTimer objects not being collected.
> > With pyqt, this is not a problem, and neither is it with a C++
> > transliteration.
> > 
> > I'm using pyside 1.2.1 on ubuntu 14.04.  My demonstration application
> > is below. 
> >
> > Am I doing something wrong?
> I just tested your example on Windows 8.0, Python 32-bit with PySide 1.2.2 
> and see no memory leak. Might be worth updating to 1.2.2 just in case, 
> otherwise it looks to be a platform specific issue.
> I don't believe you are doing anything wrong though. The QTimer should post 
> an event to the Qt Event loop, and the Python function should then end and 
> be garbage collected (along with everything in it that Python owns). The QT 
> Event loop will then run the test function again. The singleShot() method of 
> QTimer doesn't return a reference to the QTimer created anyway, so Python 
> shouldn't really be holding onto any QTimer references I would have thought.

Thanks for giving it a try.  I ended up working around the problem by
using a signal connected to a slot with a QueuedConnection, which
didn't seem to leak anything.  I'll try to update to 1.2.2 at some
point here and will report back if anything has changed.


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