Activating Batch Files from Python

[Jeff Groves]

I'm writing a launcher that should do the following:

1. Activate a .bat file to set environmental variables.
2. Start 3 programs, using said environmental variables as arguments.

However, I can't get the environmental variables to stick because all
of Pythons' system start/open functions split off into their own little
subshells, therefore the .bat file doesn't affect the main shell.

How can I use the .bat file to set environmental vars from Python?