[mod_python] DirectoryIndex index.py?

I'm starting to like mod_python, but I'm running into a bit of a problem 
with making a Python script a DirectoryIndex. I have this configuration:

AddHandler python-program .py
PythonHandler myhandler
DirectoryIndex index.py

But when I go to http://localhost/directory/, I get the Apache file 
listing. My Python handler is stored in a seprate directory, and there's 
no physical index.py file, so I'm guessing that Apache thinks there is 
no file at all. How can I get it to use my DirectoryIndex?