Managing Python code with UTF-8 (french chars) in org-mode + babel + minted for LaTeX export

The goal of this article is to illustrate how to manage Python code which includes comments in UTF-8 characters inside a latin-1 source org-mode for LaTeX export.

Note that I’ve pasted in wordpress the HTML generated by org-mode, so I hope it isn’t broken too much.

My typical use case is a french lecture on Python where the text is written in french, as well as some of the code comments and examples

We’ll use org-mode’s babel module to include and manage the Python
examples. The goal is to write the source of the Python programs
directly in the same org source as the class book’s text, and to extract them into a subdir (with the “tangle” feature), so that they can be shipped to the students to experiment with.

The minted LaTeX environment is used, for babel, to make the Python syntax highlighting.

1.1 Issues

  • The source org-mode is in latin-1 so that it compiles with pdflatex
  • The examples source-code will be in UTF-8 so that Python 2.7 executes them well on a modern Linux desktop
  • Minted relies on pygmentize wich doesn’t seem to handle UTF-8 so well

1.2 Solution

We’ll show how to “patch” minted’s use of pygmentize to take advantage
of its conversion capacity to convert the Python sources from UTF-8 to
latin-1 at document rendering time (LaTeX compilation).

It’s a hack, but works.

The current document’s source shows how this works

1.2.1 Customization

The org document should contain the following headers :

#+LANGUAGE:  fr
#+LaTeX_HEADER: \usepackage[latin1]{inputenc}
#+LaTeX_HEADER: \usepackage[french]{babel}
#+LaTeX_HEADER: \usepackage{color}\usepackage{minted}

and the footers :

# Local Variables:
# coding: latin-1
# org-src-preserve-indentation: true
# tab-width: 4
# End:

Also note that pdflatex should use the -shell-escape option necessary for minted

Now, the document should also include the following “patch” for minted :

#+LATEX_HEADER: \makeatletter
#+LATEX_HEADER: \renewcommand\minted@pygmentize[2][\jobname.pyg]{
#+LATEX_HEADER:   \def\minted@cmd{pygmentize -l #2 -f latex -F tokenmerge
#+LATEX_HEADER:     \minted@opt{gobble} \minted@opt{texcl} \minted@opt{mathescape}
#+LATEX_HEADER:     \minted@opt{startinline} \minted@opt{funcnamehighlighting}
#+LATEX_HEADER:     \minted@opt{linenos} -P "verboptions=\minted@opt{extra}"
#+LATEX_HEADER:     -O encoding=UTF-8,outencoding=iso-8859-1 -o \jobname.out.pyg #1}
#+LATEX_HEADER:   \immediate\write18{\minted@cmd}
#+LATEX_HEADER:   % For debugging, uncomment:
#+LATEX_HEADER:   %\immediate\typeout{\minted@cmd}
#+LATEX_HEADER:   \ifthenelse{\equal{\minted@opt@bgcolor}{}}
#+LATEX_HEADER:    {}
#+LATEX_HEADER:    {\begin{minted@colorbg}{\minted@opt@bgcolor}}
#+LATEX_HEADER:   \input{\jobname.out.pyg}
#+LATEX_HEADER:   \ifthenelse{\equal{\minted@opt@bgcolor}{}}
#+LATEX_HEADER:    {}
#+LATEX_HEADER:    {\end{minted@colorbg}}
#+LATEX_HEADER:   \DeleteFile{\jobname.out.pyg}}
#+LATEX_HEADER: \makeatother

The important change is the addition of the -O encoding=UTF-8,outencoding=iso-8859-1 option of pygmentize, that will convert the UTF-8 source code to latin-1.

Hopefully most of the characters will convert fine, for a document written in french.

2 Examples

2.1 Basic Python

This is a generic verbatim example, which doesn’t use babel / minted.

$ python
Python 2.7.3 (default, Jan  2 2013, 16:53:07) 
[GCC 4.7.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> print "Hello, world!"
Hello, world!
>>>

2.2 Python source code for french speakers

Here, we first include the source code, so that it can be exported to
an examples/ subdir, with the following (note that the #+ BEGIN_src / #+ END_src should be changed to get rid of the space
character between + and BEGIN / END, and that the :shebang and following text should be on the BEGIN_SRC line… I seem to have not quoted
these properly in this document):

#+name: helloworld
#+ BEGIN_src python :tangle examples/helloworld.py :noweb yes \\
:shebang #!/usr/bin/python :padline no :exports none
# -*- coding: utf-8 -*-

# Ceci est un exemple d'affichage d'une chaîne accentuée

name = raw_input("Quel est vôtre nom ? ")

print "J'espère que ça va bien aujourd'hui", name
#+ END_src

Editing it with “C-c ‘” will open an UTF-8 buffer, so hopefully, this will be consistent with the utf-8 coding system declared on the second line.

The regeneration of the examples/helloworld.py file is made with C-c C-v t (babel “tangling”).

Note that we don’t add the #!/usr/bin/python first line in the source, as we want it to be added by the tangling process (which will also make the script executable).

Once this is done, the script may be run :

$ python examples/helloworld.py 
Quel est vôtre nom ? François
J'espère que ça va bien aujourd'hui, cher François

Now, to add the colorized rendering in the lecture book, we do (here again, remove the spaces):

# +BEGIN_latex
\inputminted{python}{examples/helloworld.py}
# +END_latex

And here it is, rendered by minted:

# -*- coding: utf-8 -*-

# Ceci est un exemple d'affichage d'une chaîne accentuée

name = raw_input("Quel est vôtre nom ? ")

print "J'espère que ça va bien aujourd'hui, cher", name

Here are links to : the source, the PDF result, and the generated Python program.

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