Hi Carlo, Yep, I know about and have played with F2PY. For Ifeffit I use SWIG because I also need to be able to call Ifeffit from other C-based languages. The issue for Feff is that it is not itself suitable for calling in any manner except as a full application. The Feff6 code is not modular in any sense of the word, and relies heavily on common blocks. Also, a Feff6 calculation cannot be stopped in the middle and restarted reliably (despite what the "CONTROL" cards might imply, if feff.inp changes during a run of Feff6 the results are not easily predictable). The upshot is that it would take an enormous amount of work (including getting rid of many of the common blocks) to do any better than os.system("feff6") Anyway, that's all a separate topic.... --Matt