"Meo" <eric.paquet at isrec.ch> writes: > Somebody understand what's going on here? Yes, []*3 gives you three references to the same empty list, not three separate empty lists. You need something like [[] for i in xrange(3)] to get separate lists. Another example: a = [1,2,3] b = a a[0] = 5 print b # prints [5,2,3] Do you understand now?