ExtensionClass did include a __class_init__ class-method, which has been called at the end of class creation. I've uploaded a (simple minded) patch to fileobject.c, which implements the same behaviour for new style classes. It is simple minded because it only iterates over the tp_base member and not over tp_bases. Any chance this could be included in Python 2.2? http://sourceforge.net/tracker/index.php?func=detail&aid=478374&group_id=5470&atid=305470 Thomas