I have created a prototype of PEP 245 based on the Mobius Python library. This prototype requires no changes to Python 2.x. I have also updated PEP 245 to reflect using the prototype. Refer to the 'doc' directory for the revised PEP. The prototype can be downloaded from: http://www.zope.org/Members/michel/InterfacesPEP/Interface.tgz It contains four directories and a README that should get you started. Please follow up any comments specific to the PEP onto the type-sig@python.org list. Thanks, -Michel