Fred> For things like this, where some manner of dispatch is needed Fred> based on type, but the type itself doesn't provide some Fred> appropriate method, there's a real problem associating the right Fred> bit of code, and I'm quite torn as to the right approach to take.
Slower in some cases, but couldn't you walk up the __bases__ chain until you pop off the top or hit a match in the dispatch dict?
For stuff like the NSString stuff, perhaps adding a registration function to the marshaller would be appropriate. Of course, there's the problem coming out the other side. Does it matter if you put in a subclass of str and get out a plain old str?
Also, xmlrpclib is built to take advantage of a number of speedup helper modules. In production usage I've found it unbearably slow if used without sgmlop, for example. I'd hate to have the default situation work and have it fail if a speedup module was added to the system.