equivalent of "export" (changing parent's environment)

[Clark C . Evans]

Hello.  I have two shell scripts, a.sh and b.sh such
that a.sh calls b.sh, and b.sh uses "export key=value"
to set some defaults used later on in a.sh.

I'm now converting b.sh to python, and I can't change
a.sh easily... so I'm wondering if there is a way to
export environment variables from Python?  I've read
the documentation and see os.environ and os.putenv 
only affect the current (and sibling process) environment.

Is there an equivalent to "export" in Python?

Thanks!

Clark