Hello all! I have written a class, with the function write. The latter is defined as follows: def write(self, filename, matr, cols=self.Npred, format='asc'): blablabla return res This doesn't work. Then I changed cols=N, previously defined N=self.Npred. Now things ar ok. Why doesn't function self.some_attr in the function declaration? Grtz, Giorgi