I have finally made the 1.6 additions to python-hwloc. userdata and xml import/export od userdata works.
I spent some time trying to find a way to let userdata be a reference to a python object, but in the end decided to leave associating the userdata value with data in python space up to the user. Where in a C program you might make userdata a pointer to some structure or data area, in python you would need to put your data in a list or integer-keyed dictionary, and store the list index or dictionary key in the userdata field. As always, the git repo is at http://git.engineering.redhat.com/git/users/streeter/streeter-pyhwloc.git and rpm/srpm packages and source tarball are at http://people.redhat.com/streeter/ --Guy