Use saxon with python
A Python interface for Saxon/C is in development and worth a look:
https://github.com/ajelenak/pysaxon
There are two possible approaches:
set up an HTTP service that accepts tranformation requests and implements them by invoking Saxon from Java; you can then send the transformation requests from Python over HTTP
use the Saxon/C product
, currently available on prerelease: details here: http://www.saxonica.com/saxon-c/index.xml