calling Postgresql stored procedure (written in plpython)

[Alchemist]

Thanks for your help.

My stored procedure is written in pythonpl.  I noticed that SELECT
queries are executed correctly (results are returned to my script)
whereas UPDATE queries are not being performed as the data is not
updated.

I am using a database user with read/write access to the database.

Is there a commit statement in plpython?  (e.g. plpy.commit())
Why are UPDATEs failing?