The article recommends pkgutil.simplegeneric (1), but that's not documented anywhere. PEAK's dispatch module (2) is a better choice although there may be others out there. You can even use it to implement a familiar multimethods API (3).

1: http://svn.python.org/projects/python/trunk/Lib/pkgutil.py

2: http://peak.telecommunity.com/DevCenter/CombiningResults

3: http://bob.pythonmac.org/archives/2005/03/30/five-minute-mul...