$PYTHONDIR/site-packages/croissant/hello.py:

from mod_python import apache

def handler(req,str):
    req.content_type = "text/plain"
    req.write( str + '_handler_' )
    return apache.OK

class requester(object):
    def __init__(self, req):
        self.a='_init_'
        self.req = req

    def run(self, req):
        self.a=self.a+'_run_'
        self.env = req.subprocess_env
        return handler(req,self.a + '[' + self.env.get('REQUEST_URI') + ']' )

$HTDOCS/croissant/.htaccess:

SetHandler python-program
PythonHandler Croissant.hello::requester.run

then, http://localhost/croissant/somewhat/long/uri?insomnia=terrible results:

_init__run_[/croissant/somewhat/long/uri?insomnia=terrible]_handler_

Conclusion:
If we specify a class member as a PythonHandler, mod_python automatically instantiates the class.
We need not change httpd.conf to join a directory with mod_python. Just setup .htaccess -

Now I can roll with mod_python. ;')