Tahnk you very much for your reply.
I've tried different time with templates,but I was not able to obtain a result(cmake and make finish errors,but I suppose that swig crash,because python scripts are not able to access to any block written in C,also blocks without template)..
At the end I've solved thanks to *.t files.
Templates have also another little problem: gr_complex is declared as complex<float>,while other types are more basic..so it would be necessary to write a template for "normal" types like float,short.., plus a template of template for gr_complex
Marco