[Python-Dev] At the interactive port

[Moshe Zadka]

Continuing the recent debate about what is appropriate to the interactive
prompt printing, and the wide agreement that whatever we decide, users
might think otherwise, I've written up a patch to have the user control 
via a function in __builtin__ the way things are printed at the prompt.
This is not patches@python level stuff for two reasons:

1. I'm not sure what to call this function. Currently, I call it
__print_expr__, but I'm not sure it's a good name

2. I haven't yet supplied a default in __builtin__, so the user *must*
override this. This is unacceptable, of course.

I'd just like people to tell me if they think this is worth while, and if
there is anything I missed.

*** ../python/dist/src/Python/ceval.c	Fri Mar 31 04:42:47 2000
--- Python/ceval.c	Sat Apr 29 03:55:36 2000
***************
*** 1014,1047 ****
  		
  		case PRINT_EXPR:
  			v = POP();
! 			/* Print value except if None */
! 			/* After printing, also assign to '_' */
! 			/* Before, set '_' to None to avoid recursion */
! 			if (v != Py_None &&
! 			    (err = PyDict_SetItemString(
! 				    f->f_builtins, "_", Py_None)) == 0) {
! 				err = Py_FlushLine();
! 				if (err == 0) {
! 					x = PySys_GetObject("stdout");
! 					if (x == NULL) {
! 						PyErr_SetString(
! 							PyExc_RuntimeError,
! 							"lost sys.stdout");
! 						err = -1;
! 					}
! 				}
! 				if (err == 0)
! 					err = PyFile_WriteObject(v, x, 0);
! 				if (err == 0) {
! 					PyFile_SoftSpace(x, 1);
! 					err = Py_FlushLine();
! 				}
! 				if (err == 0) {
! 					err = PyDict_SetItemString(
! 						f->f_builtins, "_", v);
! 				}
  			}
! 			Py_DECREF(v);
  			break;
  		
  		case PRINT_ITEM:
--- 1014,1035 ----
  		
  		case PRINT_EXPR:
  			v = POP();
!                         x = PyDict_GetItemString(f->f_builtins, 
! 			                         "__print_expr__");
!                         if (x == NULL) {
!                                 PyErr_SetString(PyExc_SystemError,
!                                                 "__print_expr__ not found");
! 				Py_DECREF(v);
!                                 break;
!                         }
!                         t = PyTuple_New(1);
!                         if (t != NULL) {
! 				PyTuple_SET_ITEM(t, 0, v);
! 				w = PyEval_CallObject(x, t);
! 				Py_XDECREF(w);
  			}
! 			/*Py_DECREF(x);*/
! 			Py_XDECREF(t);
  			break;
  		
  		case PRINT_ITEM:

--
Moshe Zadka <mzadka@geocities.com>. 
http://www.oreilly.com/news/prescod_0300.html
http://www.linux.org.il -- we put the penguin in .com