extract code from code directive from restructuredtext using docutils

(I asked the following question on stackoverflow two days ago. It has not
been given any answers or even comments and very few views, so I was hoping
that it would ok to ask it again here.)

I would like to extract out the source code verbatim from code directives
in a restructuredtext string.

What follows is my first attempt at doing this, but I would like to know if
there is a better (i.e. more robust, or more general, or more direct) way
of doing it.

Let's say I have the following rst text as a string in python:

s = '''

My title
========

Use this to square a number.

.. code:: python

   def square(x):
       return x**2

and here is some javascript too.

.. code:: javascript

    foo = function() {
        console.log('foo');
    }

'''

To get the two code blocks, I could do

from docutils.core import publish_doctree

doctree = publish_doctree(s)
source_code = [child.astext() for child in doctree.children if 'code'
in child.attributes['classes']]

Now *source_code* is a list with just the verbatim source code from the two
code blocks. I could also use the *attributes* attribute of *child* to find
out the code types too, if necessary.

It does the job, but is there a better way?

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