Where does sys.path get initialized

[Jeff Epler]

It comes from the value of the PYTHONPATH environment variable, the
location of the script being executed (or the current directory, for an
interactive interpreter), an installation path or paths, and the "site"
module.  On Windows, an environment key may be involved, but I am not
aware of any specifics.

http://python.org/doc/lib/module-sys.html#l2h-352
http://python.org/doc/lib/module-site.html

Jeff