'sourcing' Python scripts?

[Haimo G. Zobernig]

Dear Python experts,

this might be a unix rather than a Python problem, but I need to set
environment variables from a Python program *in the parent process* 
that is running the Python script ( a la os.environ['BAR'] = 'foo' ).
In other words, I want to achieve the equivalent of 'sourcing' the 
Python script. Can this be done? Even better would be a solution that
also works on the various WinAbominations... (well, NT at least)

Haimo G. Zobernig

Haimo.Zobernig at cern.ch