Setting UNIX environment with a Python script

[Nom de Plume]

I connect to about 10 different servers which are various platforms,
e.g. Irix, AIX, Solaris, HP-UX.  Each has different versions of Oracle
running on it with different SIDs based on what the others are using at
my work.  Each time I want to change SIDs, I have an Oracle environment
file which I source and it sets the appropriate shell variables, e.g.
ORACLE_HOME =, etc.

I have written a little menu in Python which will determine the host
that I am connected to and present all the Oracle Environment files for
that server, along with a corresponding numeric option so that I just
have to type '3' and enter and it will set my Oracle environment for
that session.

The only step left is sourcing the ora_env.[name] file from within
Python in a way such that the environment of the parent shell is
modified.  Anyone have any ideas?  I have tried:

src_cmd = 'source ' + ora_env.file
os.system ( src_cmd )

but it doesn't like that.