On Thu, Sep 2, 2010 at 3:51 PM, Ryan May <rma...@gmail.com> wrote:
> On Sep 2, 2010, at 14:14, Benjamin Root <ben.r...@ou.edu> wrote:
>
> > There was a bug report recently (not to the mailing list) where the
> reporter noted that if an Axes3D was created using the fig.add_subplot(111,
> projection='3d') or fig.gca(projection='3d'), then you can not clear the
> figure using fig.clf(). Doing so causes an exception to be thrown.
> >
> > Tracing down the problem revealed that the Axes3D object was added twice
> to the figure's self.axes, but exists only once in self._axstack. So, when
> looping through self.axes, a delete is attempted on an axes that no longer
> exists in the stack.
> >
> > I traced down the cause for why the axes is added twice. Because of how
> Axes3D used to be attached to a figure (and is still valid), the __init__()
> function for Axes3D calls figure.add_axes(self) on its own. This
> initialization is done after the check in add_subplot to see if the axes
> exists already in the figure. So, add_subplot then adds the axes without
> knowing that it already happened.
> >
> > I think there are multiple issues here. Primarially, there is the issue
> that Axes3D is attaching itself to a figure. However, in the interest of
> backwards-compatibility, we can't just fix this outright. There is also the
> issue that there are multiple places in the Figure class that are adding
> axes to the figure object. Ideally, shouldn't we have a single function
> that performs proper checks and adds an axes? Then that function should be
> used in the other class functions to perform this action. In my opinion,
> there is too much duplicated code here.
>
> I agree the duplicated code should be eliminated. Depending on how complex
> it would be to clean that up and not break existing code, could we in the
> short term make use of sets to eliminate duplicates?
>
> Ryan
I am not exactly sure how possible that would be. I am not exactly sure I
understand the rationale behind the current implementation. There is a
dictionary self._seen that stores key/axes pairs, a self.axes list storing
the axes, and a self._axstack Stack (from cbook, I believe) that also
contains the axes.
I think I understand the purpose for each container by itself, but not for
having all three together at the same time. At the very least, maybe we can
eliminate the list container? I think the difficulty there would be with
clearing the stack properly.
Ben Root
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