[matplotlib-devel] Qt close bug revisited

[Tony Yu <ts...@gm...>]

I'm getting a strange error when multiple figures are created *without a
call to show*. Here's the traceback:

Traceback (most recent call last):
  File
"/Users/Tony/python/devel/mpl/lib/matplotlib/backends/backend_qt4.py", line
151, in <lambda>
    lambda: self.close_event())
  File "/Users/Tony/python/devel/mpl/lib/matplotlib/backend_bases.py", line
1564, in close_event
    self.callbacks.process(s, event)
AttributeError: 'FigureCanvasQTAgg' object has no attribute 'callbacks'


Here's a simple test case:

import matplotlib.pyplot as plt
fig = plt.figure()
plt.plot([0, 1])
fig = plt.figure()
plt.plot([0, 1])


This issue appears in versions after the PR to fix the Qt4 close
bug<https://github.com/matplotlib/matplotlib/pull/716>.
The error occurs even without the `plot` calls, but the failures aren't as
consistent (the error will randomly disappear).

Note that sticking a call to `plt.show()` at the end and then manually
closing the figures does not seem to produce this error. I'm having a
difficult time locating the source of the bug: when I stick a pdb trace in
the code, the error doesn't get raised.

Can anyone reproduce this issue?

-Tony