How to access to the root path in a mod_python directory?

<Directory /var/www/MYDOMAIN.com/htdocs>
    SetHandler mod_python
    PythonHandler mod_python.publisher
    PythonDebug On
</Directory>

from mod_python import apache

def requesthandler(req):
    req.content_type = "text/plain"
    req.write("Hello World!")
    return apache.OK

DirectoryIndex index