hello, It's the problem >>>d1=[[0,0]] >>>d2=d1 #reference no copy >>>d2[0][0]=3 >>>d2 [[3,0]] >>>d1 [[3,0]] ok but, >>>d1=[[0,0]] >>>d2=d1[:] #copy, no reference >>>d2[0][0]=3 >>>d2 [[3,0]] >>>d1 [[3,0]] Why, is copy, no reference How copy a object? Excluse me, my english Gracias (Thank's), Saludos, Roland