Appending to sys.path

[mhearne808[insert-at-sign-here]gmail[insert-dot-here]com]

I have an application where I would like to append to the python path
dynamically.  Below is a test script I wrote.  Here's what I thought
would happen:

1) I run this script in a folder that is NOT already in PYTHONPATH
2) The script creates a subfolder called foo.
3) The script creates a file called foo.py, with a foo() method
defined in it.
4) The script attempts to import this module, which fails because the
current folder is not in PYTHONPATH.
5) The script then adds the current folder to the end of sys.path
6) The script again attempts to import foo.foo, and succeeds.

#6 never happens, but I can't figure out why.  I'm running on Mac OS
10.5, with python 2.5.1.

Anybody have any tips?

Thanks,

Mike

Here's the script:
#!/usr/bin/python

import sys
import os.path

txt = 'def foo(): print "Hello world!"\n'
if not os.path.isdir('foo'):
    os.mkdir('foo')
f = open('foo/foo.py','wt')
f.write(txt)
f.close()

try:
    __import__('foo.foo')
except ImportError:
    homedir = os.path.abspath(sys.path[0]) #where is this script?
    print 'Adding %s to sys.path' % (homedir)
    sys.path.append(homedir)
    try:
        __import__('foo.foo')
        print 'Import now successful'
    except ImportError:
        print "Why didn't this work?"
        sys.exit(1)