#+NAME: test2
#+begin_src python :results value :preamble # -*- coding: utf-8 -*- :return
a
a = ( ( "é", "a" ), ( "a", "à" ) )
b = "é"
#+end_src
#+RESULTS: test2
| \303\251 | a |
| a | \303\240 |
Maybe this isn't an execution problem, but is rather a buffer encoding
problem. I executed your example above in a small buffer (attached). I
then saved this buffer and was forced to specify an encoding, I selected
utf8. If I cat the resulting file from disk, the accented characters
appear correctly.
So maybe the problem is simply Emacs not displaying utf8 characters
correctly.
Hope this helps,