Using Python within LaTeX and accessing its variables

Question

I have used the python package to include Python in my LaTeX document which works fine.

I am trying to access the Python variables/calculations outside of \begin{python} ... \end{python}, without luck.

My question is: Can I? or How do I access variables/calculations within Python code embedded in LaTeX?

Simple example

\begin{python}
tdegc = 25.0
tdegf = (tdegc - 32.0)/1.0
print 'T in DegC is ', tdegc , ' in Deg F is ', tdegf
\end{python}

My calculations show that $\mbox{tdegf} = $ tdegf (this is the value for tdegf)

Answer 1

I've played around a little with the sagetex package (designing tests which can be randomized) and I think you should look into its documentation. sagetex allows you incorporate Sage into your LaTeX code. Since Sage is based Python, you can run Python using sagetex. There is a \sage command that lets you jump back in to work with variables you've defined before, which I think is the issue you are concerned about. You can find some examples on CTAN. Here's a cut down sample:

\documentclass[10pt]{article} 
\usepackage{sagetex} 

\begin{document} 
\begin{sagesilent}%use sage without producing output
n, x = var('n x')
a = ZZ.random_element(-10,10)
while a == 0:
   a = ZZ.random_element(-10,10)
b = ZZ.random_element(-10,10)
c = ZZ.random_element(-10,10)
d = ZZ.random_element(2,9)
ratexp1 = (a*n)/(a*n+1)
ratexp2 = (d**(d*n-1))/((d+1)**n)
ratexp3 = 1/(a*x+b)
deriv1 = diff(ratexp3,x,1)
\end{sagesilent}
\begin{enumerate} %creates the numbering for the problems.
\item $\Sigma_{n=1}^{\infty} \sage{ratexp2}$

\vskip 2 in %leaves 2 inches of space for student work
\item Find the derivative of $\sage{ratexp3}$. The answer is $\sage{deriv1}$

\vskip 2 in %leaves 2 inches of space for student work
\item Consider the series: $ \Sigma_{n=1}^{\infty}\sage{ratexp1} $
Find a formula for $s_n$, the nth partial sum. 
\end{enumerate}
\end{document}

The code is choosing random elements for a,b,c,d but throws out a if a=0. I then defined rational expressions (to be used in the problems) and even calculated a derivative. At that point, I left Sage but I can still access the past work (even in math mode) using the \sage command; eg. \sage{ratexp2}.

Note: although I used a = ZZ.random_element(-10,10) to produce random integers, you can use the typical Python commands to produce random numbers. You'll also need to install Sage, along with the style file. Just like the python package, compiling the code produces an intermediate file (.sage file) which you process with Sage. sagetex is a very powerful package.

Answer 2

^{This is too long to be a comment, since the OP's intent is not 100% clear.}

There is usually very little in terms of interaction between environments used and whatever is contained within them that can be used outside of that environment. Typically, environments are used to format its contents in a general way, performing certain operations at the start of the environment (at \begin{<env>}) and some at the end (at \end{<env>}).

If you're interested in performing calculations within your document, or at least mimic it without going through the trouble of specifying things verbatim, the fp package provides floating point operations at compile time. Here is a short example:

\documentclass{article}
\usepackage[nomessages]{fp}% http://ctan.org/pkg/fp
\newcommand{\degrees}[1][C]{{}^\circ\mathrm{#1}}% degrees celcius/fahrenheit
% Celcius <-> Fahrenheit conversions: http://en.wikipedia.org/wiki/Fahrenheit
\begin{document}
Some temperature conversions:
\begin{itemize}
  \item \FPeval{\result}{round((89.2-32)*(5/9),1)}%
    $89.2\degrees[F]=\result\degrees$
  \item \FPeval{\result}{round(25*(9/5)+32,1)}%
    $25\degrees=\result\degrees[F]$
\end{itemize}
\end{document}

As a result, it is now possible to include python code in your document and you could use inline fp code (outside the python environment) to calculate expressions that you can typeset in your document.

Answer 3

There is also SympyTeX, a package that allows you to use the complete functionality of python and sympy within your LaTeX document.

Here is an example: Using sympy within your LaTeX document is as easy as $2+2=\sympy{2+2}$.

You can write a block, and then use the variables defined later in your code!
\begin{sympyblock}
    x = sympy.Symbol('x')
    h = sympy.integrate(1+x,x)
\end{sympyblock}
The variable $h$, how can be called using {\verb \sympy{h} }, and you will get $h =  
\sympy{h}$. Similarly, the integral of $1+x^4$ is $\sympy{sympy.integrate(1+x**4,x)}$.

This will result in:

As far as I know it is not yet available on CTAN but you can download it from the author's homepage: SympyTeX