Implementation of PEP-0217.

This closes the PEP, and patch 103170

diff --git a/Doc/lib/libsys.tex b/Doc/lib/libsys.tex
index 2fda26e429c3aa356c1a8a755f3765b8b6ce9a7d..df32182e666b7f3e7acd3f201bb4ca360e69d1b2 100644 (file)
--- a/Doc/lib/libsys.tex
+++ b/Doc/lib/libsys.tex
@@ -44,6 +44,15 @@ Integer specifying the handle of the Python DLL.
 Availability: Windows.
 \end{datadesc}
 
+\begin{funcdesc}{displayhook}{\var{value}}
+If \var{value} is not \code{None}, this function prints it to 
+\code{sys.stdout}, and saves it in \code{__builtin__._}.
+
+This function is called when an expression is entered at the prompt
+of an interactive Python session. It exists mainly so it can be
+overridden.
+\end{funcdesc}
+
 \begin{funcdesc}{exc_info}{}
 This function returns a tuple of three values that give information
 about the exception that is currently being handled.  The information

diff --git a/Python/ceval.c b/Python/ceval.c
index 5110746441d57f941d55b71ace55188eb6a8f221..8012b8357f2eacae7e9e1561bcdc6970221b79b0 100644 (file)
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -1245,36 +1245,26 @@ eval_code2(PyCodeObject *co, PyObject *globals, PyObject *locals,
 
                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);
-                               }
+                       w = PySys_GetObject("displayhook");
+                       if (w == NULL) {
+                               PyErr_SetString(PyExc_RuntimeError,
+                                               "lost sys.displayhook");
+                               err = -1;
+                       }
+                       if (err == 0) {
+                               x = Py_BuildValue("(O)", v);
+                               if (x == NULL)
+                                       err = -1;
+                       }
+                       if (err == 0) {
+                               w = PyEval_CallObject(w, x);
+                               if (w == NULL)
+                                       err = -1;
                        }
                        Py_DECREF(v);
+                       Py_XDECREF(x);
                        break;
-               
+
                case PRINT_ITEM_TO:
                        w = stream = POP();
                        /* fall through to PRINT_ITEM */

diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 33d71ac1d8f6c4ac7c862deaf558c85f6fd4af03..037b567f33a2f046373f14d65d006a0105dd97e8 100644 (file)
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -67,6 +67,50 @@ PySys_SetObject(char *name, PyObject *v)
                return PyDict_SetItemString(sd, name, v);
 }
 
+static PyObject *
+sys_displayhook(PyObject *self, PyObject *args)
+{
+       PyObject *o, *stdout;
+       PyInterpreterState *interp = PyThreadState_Get()->interp;
+       PyObject *modules = interp->modules;
+       PyObject *builtins = PyDict_GetItemString(modules, "__builtin__");
+
+       /* parse arguments */
+       if (!PyArg_ParseTuple(args, "O:displayhook", &o))
+               return NULL;
+
+       /* Print value except if None */
+       /* After printing, also assign to '_' */
+       /* Before, set '_' to None to avoid recursion */
+       if (o == Py_None) {
+               Py_INCREF(Py_None);
+               return Py_None;
+       }
+       if (PyObject_SetAttrString(builtins, "_", Py_None) != 0)
+               return NULL;
+       if (Py_FlushLine() != 0)
+               return NULL;
+       stdout = PySys_GetObject("stdout");
+       if (stdout == NULL) {
+               PyErr_SetString(PyExc_RuntimeError, "lost sys.stdout");
+               return NULL;
+       }
+       if (PyFile_WriteObject(o, stdout, 0) != 0)
+               return NULL;
+       PyFile_SoftSpace(stdout, 1);
+       if (Py_FlushLine() != 0)
+               return NULL;
+       if (PyObject_SetAttrString(builtins, "_", o) != 0)
+               return NULL;
+       Py_INCREF(Py_None);
+       return Py_None;
+}
+
+static char displayhook_doc[] =
+"displayhook(o) -> None\n"
+"\n"
+"Print o to the stdout, and save it in __builtin__._\n";
+
 static PyObject *
 sys_exc_info(PyObject *self, PyObject *args)
 {
@@ -332,6 +376,7 @@ extern PyObject *_Py_GetDXProfile(PyObject *,  PyObject *);
 
 static PyMethodDef sys_methods[] = {
        /* Might as well keep this in alphabetic order */
+       {"displayhook", sys_displayhook, 1, displayhook_doc},
        {"exc_info",    sys_exc_info, 1, exc_info_doc},
        {"exit",        sys_exit, 0, exit_doc},
        {"getdefaultencoding", sys_getdefaultencoding, 1,
@@ -475,6 +520,7 @@ __stderr__ -- the original stderr; don't use!\n\
 \n\
 Functions:\n\
 \n\
+displayhook() -- print an object to the screen, and save it in __builtin__._\n\
 exc_info() -- return thread-safe information about the current exception\n\
 exit() -- exit the interpreter by raising SystemExit\n\
 getrefcount() -- return the reference count for an object (plus one :-)\n\