Re: [Matplotlib-users] Segmentation faults with show() in ipython

Cory Davis wrote:
> Hi All,
> some time ago I lost the ability to plot anything from within ipython. 
> For example ...
> 
> In [1]:from pylab import *
> 
> In [2]:plot(range(20),range(20))
> ---------------------------------------------------------------------------
> exceptions.SystemError                               Traceback (most 
> recent call last)
> 
> 
> SystemError: Objects/moduleobject.c:48: bad argument to internal function
> Segmentation fault
> 
> The above occurs both with "ipython -pylab" and also "ipython" with the 
> ahow() command at the end.  Thankfully everything works with the vanilla 
> python interpreter.
> 
> Its possible that this became broken after changing my OS to Redhat EL4. 
>   Updating to the SVN version of ipython has not helped.
> I have python 2.3.4, and matplotlib 0.83.2
> 
> Has anyone seen anything like this?

I have: it's a GTK-backend only bug, as far as I've seen.  I normally don't 
use GTK, so it doesn't bother me too much.  You can work around the problem by 
switching to any other backend (TkAgg, WXAgg, QtAgg will all do).

> Any advice?

The problem is _extremely_ strange, and the nastiest part is that John hasn't 
been able to see it.  I even gave him an account on one of my local system, 
and the bug doesn't appear for him when SSH'd into Colorado from Chicago (he 
can display plot windows over X11), though I do see it logged in as his user 
at the console.

This can't be explicitly an ipython bug, since ipython is pure python code (so 
it can't segfault by itself), but it's most likely a threading problem 
triggered by ipython.  John and I are at a loss as to what can be going on 
here, and any ideas would be most welcome.

I may try to dig deeper into it, but since I don't know my way around the 
pygtk and maptlotlib gtk codes, I'm not terribly hopeful (and it won't be done 
until I clear the big backlog of ipython issues I have on my plage).

Sorry not to be able to offer a better answer right now...

Regards,

f