Sorry for this question, but I am just puzzled. Why does print [4,1,3,2].sort() just print None ? As far as I understood the docs 'sort' should take 'cmp' for comparisons which is well defined for integers. Thanks for a hint, Helmut Jarausch Lehrstuhl fuer Numerische Mathematik RWTH - Aachen University D 52056 Aachen, Germany