Hi Samuele, with your help, I can now handle my extra fields in arbitrary instances very well. One problem remains: (see test_wrapping) The support function is no longer a simple thing, but it contains a decision, so I need two blocks. In test_wrapper, I solved this by making wrap_obj a high level function, which first tries fetch_pywrapper and then create_pywrapper. This works fine. In the real implementation, I don't have this chance, because convert_from_to is an rtyper function, and I can't call something high level that does it for me. Q: Do I need hlinvoke for this, or is there a better way? thanks & cheers - chris -- Christian Tismer :^) <mailto:tismer@stackless.com> tismerysoft GmbH : Have a break! Take a ride on Python's Johannes-Niemeyer-Weg 9A : *Starship* http://starship.python.net/ 14109 Berlin : PGP key -> http://wwwkeys.pgp.net/ work +49 30 802 86 56 mobile +49 173 24 18 776 fax +49 30 80 90 57 05 PGP 0x57F3BF04 9064 F4E1 D754 C2FF 1619 305B C09C 5A3B 57F3 BF04 whom do you want to sponsor today? http://www.stackless.com/