The Zope developers have ripped out the ZClasses functionality from the Zope core in version 2.12. As promised, I have collected the former code in a new package ("dm.zopepatches.zclasses" on PyPI). When imported, this package uses monkey patching to restore the ZClasses functionality. New tests verify the functionality as formerly described in the Zope book (2.7 edition). To make "ZClasses" available again, the ZODB root database requires "dm.zopepatches.zclasses.ClassFactory" as "class-factory" option in the Zope configuration file. When this option is processed, the package is imported and the monkey patching takes place. The current version does not yet restore the "distribution" functionality (of Zope products). Let me know when you need this functionality. -- Dieter