[Matplotlib-users] Avoid circular references with format_coord and Qt?

[Sebastian B. <seb...@si...>]

Hey,

probably there is nothing to help me here, but I have a QtGui, using
matplotlib and basically end up in a circular reference hell that is not
resolvable by the gc. After removing almost all circular references, the
python inherited QWidget that embeds the figurecanvas is now deleted
fine.

The thing I end up with however is something like

class Visualize(object):
     def __init__(self):
         self.figure = Figure()
         canvas = FigureCanvas(self.figure)
         PythonInheritedQtWidget(self).element.setWidget(canvas)
         
         def format(*args):
             # do stuff
             return something         
         self.axis = self.figure.add_subplot(1, 1, 1) 
         self.axis.format_coord = format

         # This was completely drawn with canvas and all
         # PythonInheritedQtWidget is deleted fine.

I have not been able to get a minimal test case. But I have it pinned
down that everything can get cleaned up after:

del Visualize.axes.format_coord

so the circular reference that makes it not collectable is only the
format_coord which is a method pointing to the class owning the figure
and the axis. I am about to just use a weak reference wrapper function
to break the circle but it seems silly.

Anyway, I do not expect that anyone can help, and I expect it is some Qt
stuff really, but this is seriously annoying me....

- Sebastian