Re: [Matplotlib-users] FigureCanvasQTAgg clean up

[Mads I. <mad...@gm...>]

On 01/30/2013 05:03 PM, Benjamin Root wrote:
>
>
> On Tue, Jan 29, 2013 at 5:12 PM, Mads Ipsen <mad...@gm... 
> <mailto:mad...@gm...>> wrote:
>
>     Hi,
>
>     I spend some time writing up the question below on Stackoverflow
>     which immediately was closed as a duplicate of other posts. To my
>     best knowledge, these posts did not answer my questions - so I'll
>     try my luck here instead:
>
>     I am using the qt backengine for setting up a QWidget that embeds
>     a matplotlib scene. When the widget is closed it appears that many
>     of the matplotlib objects that were part of the plot still are
>     alive in Python space.
>
>     My question is basically the following: What actions should I take
>     to clean up the figure and axes objects etc. that were part of the
>     plot widget? The qt backend comes with a figure manager, but it
>     appears a little unclear how it should be used.
>
>     I have attached a small unit test example that sets up a plot.
>     When the plot appears, just close it, and the test will garbage
>     collects the plot, and then display info of the matplotlib objects
>     that are still alive in Python space. Clearly both the path of the
>     plot, and several Bbox objects are still referenced.
>
>     Our current unit test suite contains almost 10000 GUI tests and
>     its imperative that proper object space clean up is done after
>     each test. Any help is much appreciated.
>
>     Best regards,
>
>     Mads
>
>
> Would "fig.clf()" do what you need?
>
> Ben Root
>
Thanks for the feedback.

The trick is to get this done automatically when the widget is closed. 
If you look in backend_qt4.py in the constructor of FigureCanvasQT 
you'll find

   QtCore.QObject.connect(self, QtCore.SIGNAL('destroyed()'), 
self.close_event)

which should perform the steps below when close_event is called

   event = CloseEvent(s, self, guiEvent=guiEvent)
   self.callbacks.process(s, event)

If I insert print statements, the signal is ignored with matplotlib 
1.1.0, but called with 1.2.0 (which uses a lambda function in the above 
connection).But inspecting pythons objects after the close() method is 
called on the widget, it seems that - at least - the paths associated 
with plot actually still exist.

So I'm just a bit worried if there already is existing functionality in 
the FigureCanvasQTAgg object that can do these things for me. And if so, 
how to use them?

Best regards,

Mads




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