Yes, these are bytecode files. If you run "python -o", you should also get .pyo files for optimized bytecode. As long as you do not modify the source code, python directly reuse the bytecode (that's also a way to distribute script without source code to avoid your users fiddling in thecode and make it not work properly - even if any advanced user will know how to revert back to source code)
-- http://mail.python.org/mailman/listinfo/python-list
