Hi the string constant r'\\' produces the illegal C string "\\\" It's easy to work around, just use '\\' Thanks for Pyrex, it's great I've just used it as a 'compiler' for Python code. I only had to replace 'x+= 1' by x= x+1 Helmut -- Helmut Jarausch Lehrstuhl fuer Numerische Mathematik RWTH - Aachen University D 52056 Aachen, Germany