Re: [Matplotlib-users] Displaying \frac{a}{b} in xlabel

[Ryan K. <rya...@gm...>]

I think I got it.  I had to play around a bit with a couple different
approaches.  Part of the trick is that you have to run latex with
-interaction=3Dnonstopmode, otherwise the child process never completes
and it seems like most of python's tools for capturing the errors and
outputs just hang.

Here is what I did:
import popen2
In [8]: latexcmd3=3Dpopen2.Popen3('latex -interaction=3Dnonstopmode bad.tex=
')

In [9]: latexcmd3.wait()
Out[9]: 256

In [10]: latexcmd4=3Dpopen2.Popen3('latex -interaction=3Dnonstopmode good.t=
ex')

In [11]: latexcmd4.wait()
Out[11]: 0

where bad.tex and good.tex basically have just headers and
\frac{1}{\theta} with and without $$ around it.  If I just use
os.popen3, the stderr object returned is empty in both cases:

In [14]: r,w,e=3Dos.popen3('latex -interaction=3Dnonstopmode good.tex')

In [15]: e.readlines()
Out[15]: []

In [16]: r,w,e=3Dos.popen3('latex -interaction=3Dnonstopmode bad.tex')

In [17]: e.readlines()
Out[17]: []

and to know there was a problem, you would have to parse w.readlines()
- and in this case it doesn't even say there is an error, it mentions
something about a missing $.

But it seems like creating your own Popen3 object and executing it
through the wait() command, returns 0 on a clean exit or 256 on the
bad ones (at least for this error).  I have compiled one other good
file from my hard drive and it also returns 0.

Hope this helps,

Ryan

On 3/8/06, Darren Dale <dd...@co...> wrote:
> >> On Wednesday 08 March 2006 5:06 am, Nils Wagner wrote:
> >>
> >>> Hi all,
> >>>
> >>> How do I use \frac{a}{b} within labels ?
> >>>
> >>> from pylab import *
> >>> from scipy import *
> >>> x =3D linspace(0,pi,20)
> >>> plot(x,sin(x))
> >>> title(r'\frac{\Theta}{2\pi}')
> >>> xlabel(r'\frac{\Theta}{2\pi}') # The output is not o.k.
> >>> show()
> >>>
> >>> Am I missing something or is it a bug ?
> >>>
> >>
> >> What does "The output is not o.k." mean?
> >>
> > The output is somewhat like \Theta \frac{}{2\pi}
> > If I use
> > xlabel(r'$\frac{\Theta}{2\pi}$')
> >
> > it works fine.
>
> This is not a bug. Please keep in mind that usetex is really only an inte=
rface
> to latex. For problems specific to LaTeX, it would be best to consult the
> appropriate sources or lists. As it happens, \frac is only allowed in mat=
h
> mode. That it produced any output at outside of mathmode is a case of fai=
ling
> silently.
>
> Does anyone know how to catch exit status using os.popen and friends? LaT=
eX
> would have returned an exit status of 1 for this example, which could be =
used
> to raise a warning.
>
> Darren
>
>
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