[Matplotlib-users] BUG: RuntimeError: dictionary changed size during iteration

[Massimiliano C. <mas...@ms...>]

Hello everyone,

in my program I'm encountering an error when calling the function axes.set_xticks (Matplotlib 1.2.0 on python 2.7-64 bit). It is really difficult for me to build a test case, because my program is really complex. Here is the error traceback:

File "C:\Python27\Lib\site-packages\matplotlib\axes.py", line 2596, in set_xticks
  return self.xaxis.set_ticks(ticks, minor=minor)
File "C:\Python27\Lib\site-packages\matplotlib\axis.py", line 1489, in set_ticks
  self.set_view_interval(min(ticks), max(ticks))
File "C:\Python27\Lib\site-packages\matplotlib\axis.py", line 1771, in set_view_interval
  max(vmin, vmax, Vmax))
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 932, in _set_intervalx
  self.invalidate()
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 131, in invalidate
  return self._invalidate_internal(value, invalidating_node=self)
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 155, in _invalidate_internal
  invalidating_node=self)
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 155, in _invalidate_internal
  invalidating_node=self)
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 155, in _invalidate_internal
  invalidating_node=self)
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 2141, in _invalidate_internal
  invalidating_node=invalidating_node)
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 155, in _invalidate_internal
  invalidating_node=self)
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 2141, in _invalidate_internal
  invalidating_node=invalidating_node)
File "C:\Python27\Lib\site-packages\matplotlib\transforms.py", line 153, in _invalidate_internal
  for parent in self._parents.itervalues():
File "C:\Python27\Lib\weakref.py", line 147, in itervalues
  for wr in self.data.itervalues(): 
RuntimeError: dictionary changed size during iteration

I googled and found that this is a well known bug due to the use of self.data.itervalues() in the for loop (i think the correct syntax should be for wr in iter(self.data.items()). So I would like to point out the bug (if it is) to the matplotlib guys, how can I do it?
In the meantime, how can I work around it without changing the source code?
Thanks in advance!