The problem is that if no display is available, the error gets raised on the
point where I try to create a new figure, long before getting to show(), so I
can't do anything at all. Here's what it looks like when I log in without a
display available:
>>> import matplotlib.pyplot as plt
>>> plt.figure()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File
"/usr/local/Python/Versions/2.6.5/lib/python2.6/site-packages/matplotlib/pyplot.py",
line 270, in figure
**kwargs)
File
"/usr/local/Python/Versions/2.6.5/lib/python2.6/site-packages/matplotlib/backends/backend_tkagg.py",
line 83, in new_figure_manager
window = Tk.Tk()
File "/usr/local/Python/Versions/2.6.5/lib/python2.6/lib-tk/Tkinter.py", line
1643, in __init__
self.tk = _tkinter.create(screenName, baseName, className, interactive,
wantobjects, useTk, sync, use)
_tkinter.TclError: no display name and no $DISPLAY environment variable
I can do this, which is widely recommended:
>>> import matplotlib
>>> matplotlib.use('Agg')
>>> import matplotlib.pyplot as plt
>>> fig=plt.figure()
>>> fig.save_fig('test.png')
But as far as I can tell from searching, once you do this, there is no way to
display to the screen. Unless there is a very clever trick that I don't know
about... which I am asking for here... :-)
On Jan 26, 2011, at 11:16 PM, Benjamin Root wrote:
> On Wednesday, January 26, 2011, David Perlman <dperl...@wisc.edu> wrote:
>> I'm trying to make a simple utility for doing a quick check of some data
>> (electrophysiology recordings from our fMRI scanner lab). I want it to be
>> foolproof as much as possible, so I was trying to figure out how to write a
>> script that would try to plot to the display, then if that didn't work, to
>> save it to a file instead (preferably as pdf, but I could live with png if
>> that was the only option.)
>>
>> I've been searching the documentation and code examples for a while, and all
>> I can find seems to suggest that the choice of display vs. file is
>> predetermined at the very beginning by the choice of backend. I suppose
>> that would mean I'd have to put the whole thing inside a try block, then if
>> that didn't work, start over from scratch with a different backend and build
>> the plot again. I was hoping to find a way to build the plot, then just try
>> to "show" it or something like that, and if that failed, then save it
>> instead. But so far I have not been able to figure out such a thing. So I
>> would appreciate any help! Thanks very much!
>>
>>
>
> You can always put the show call in a try block and do a savefig if
> the show fails. I don't know where you get the idea that you have to
> do one or the other...
>
> Unless you are talking about the issue where the closing of a figure
> window would cause you to lose the figure data? In which case, you
> should be fine catching the show and doing the savefigg because the
> close event never occurred. However, you might get messy this way with
> a blank figure window...
>
> To be "foolproof" I would just always save first and then attempt to
> show. If the show was successful, you can delete the saved figure.
>
> Sorry for the rambling, but those are my thoughts on it.
>
> Ben Root
--
-dave----------------------------------------------------------------
"Pseudo-colored pictures of a person's brain lighting up are
undoubtedly more persuasive than a pattern of squiggles produced by a
polygraph. That could be a big problem if the goal is to get to the
truth." -Dr. Steven Hyman, Harvard
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