[Matplotlib-users] WXAgg Backend Errors on Exit

[A. S. B. <ab...@gm...>]

Dear all,

I have been using the WXAgg backend with matplotlib and have been
coming across an occasional error.  Unfortunately, it is a little
difficult to trap as it doesn't happen every time!  Running on Windows
with python 2.5.2, matplotlib 0.98.0 (installed from the binary) and
wx version 2.8.7.1 (msw-unicode), I have produced the error by
creating two figures as follows:

from pylab import *

t = arange(-4*pi,4*pi,0.1)
y = sin(t)/t
figure()
plot(t,y)
figure()
plot(t,y*y)
show()

The script works correctly, but when the two figure windows are
closed, I get the error messages shown at the end of this email.
Commenting out the second figure() and plot() lines seems to stop the
error from appearing.  It is important to note, however, that this may
not be the direct cause as the error doesn't always appear even with
both pairs of figure() and plot() lines in.

I have also tried replacing show() with:

try:
    show()
except:
    print "Caught exception"

but no exception is caught and the error message still appears.

Has anyone got any thoughts on this please?

Al

Error:

Traceback (most recent call last):
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backends\backend_wx.py",
line 1126, in _onMotion
    FigureCanvasBase.motion_notify_event(self, x, y, guiEvent=evt)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 939, in motion_notify_event
    self.callbacks.process(s, event)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\cbook.py",
line 152, in process
    func(*args, **kwargs)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 1358, in mouse_move
    if self._lastCursor != cursors.POINTER:
  File "C:\programs\development\python25\lib\site-packages\wx-2.8-msw-unicode\wx\_core.py",
line 14318, in __getattr__
    raise PyDeadObjectError(self.attrStr % self._name)
wx._core.PyDeadObjectError: The C++ part of the
NavigationToolbar2WxAgg object has been deleted, attribute access no
longer allowed.
Traceback (most recent call last):
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backends\backend_wx.py",
line 1126, in _onMotion
    FigureCanvasBase.motion_notify_event(self, x, y, guiEvent=evt)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 939, in motion_notify_event
    self.callbacks.process(s, event)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\cbook.py",
line 152, in process
    func(*args, **kwargs)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 1358, in mouse_move
    if self._lastCursor != cursors.POINTER:
  File "C:\programs\development\python25\lib\site-packages\wx-2.8-msw-unicode\wx\_core.py",
line 14318, in __getattr__
    raise PyDeadObjectError(self.attrStr % self._name)
wx._core.PyDeadObjectError: The C++ part of the
NavigationToolbar2WxAgg object has been deleted, attribute access no
longer allowed.
Traceback (most recent call last):
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backends\backend_wx.py",
line 1126, in _onMotion
    FigureCanvasBase.motion_notify_event(self, x, y, guiEvent=evt)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 939, in motion_notify_event
    self.callbacks.process(s, event)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\cbook.py",
line 152, in process
    func(*args, **kwargs)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 1358, in mouse_move
    if self._lastCursor != cursors.POINTER:
  File "C:\programs\development\python25\lib\site-packages\wx-2.8-msw-unicode\wx\_core.py",
line 14318, in __getattr__
    raise PyDeadObjectError(self.attrStr % self._name)
wx._core.PyDeadObjectError: The C++ part of the
NavigationToolbar2WxAgg object has been deleted, attribute access no
longer allowed.
Traceback (most recent call last):
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backends\backend_wx.py",
line 1126, in _onMotion
    FigureCanvasBase.motion_notify_event(self, x, y, guiEvent=evt)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 939, in motion_notify_event
    self.callbacks.process(s, event)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\cbook.py",
line 152, in process
    func(*args, **kwargs)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 1358, in mouse_move
    if self._lastCursor != cursors.POINTER:
  File "C:\programs\development\python25\lib\site-packages\wx-2.8-msw-unicode\wx\_core.py",
line 14318, in __getattr__
    raise PyDeadObjectError(self.attrStr % self._name)
wx._core.PyDeadObjectError: The C++ part of the
NavigationToolbar2WxAgg object has been deleted, attribute access no
longer allowed.
Traceback (most recent call last):
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backends\backend_wx.py",
line 1126, in _onMotion
    FigureCanvasBase.motion_notify_event(self, x, y, guiEvent=evt)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 939, in motion_notify_event
    self.callbacks.process(s, event)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\cbook.py",
line 152, in process
    func(*args, **kwargs)
  File "C:\programs\development\python25\Lib\site-packages\matplotlib\backend_bases.py",
line 1358, in mouse_move
    if self._lastCursor != cursors.POINTER:
  File "C:\programs\development\python25\lib\site-packages\wx-2.8-msw-unicode\wx\_core.py",
line 14318, in __getattr__
    raise PyDeadObjectError(self.attrStr % self._name)
wx._core.PyDeadObjectError: The C++ part of the
NavigationToolbar2WxAgg object has been deleted, attribute access no
longer allowed.