Optimize common case for dict.fromkeys().

diff --git a/Objects/dictobject.c b/Objects/dictobject.c
index 00f9bc8b2fa100cab1faa273f4ac90f2c2998b89..978071b1c1cbc5c5296b762ec29247ca250dee41 100644 (file)
--- a/Objects/dictobject.c
+++ b/Objects/dictobject.c
@@ -1191,7 +1191,7 @@ dict_fromkeys(PyObject *cls, PyObject *args)
                PyObject *key;
                long hash;
 
-               if (dictresize(mp, ((PyDictObject *)seq)->ma_used))
+               if (dictresize(mp, PySet_GET_SIZE(seq)))
                        return NULL;
 
                while (_PyDict_Next(seq, &pos, &key, &oldvalue, &hash)) {
@@ -1227,19 +1227,24 @@ dict_fromkeys(PyObject *cls, PyObject *args)
                return NULL;
        }
 
-       for (;;) {
-               key = PyIter_Next(it);
-               if (key == NULL) {
-                       if (PyErr_Occurred())
+       if (PyDict_CheckExact(d)) {
+               while ((key = PyIter_Next(it)) != NULL) {
+                       status = PyDict_SetItem(d, key, value);
+                       Py_DECREF(key);
+                       if (status < 0)
+                               goto Fail;
+               }
+       } else {
+               while ((key = PyIter_Next(it)) != NULL) {
+                       status = PyObject_SetItem(d, key, value);
+                       Py_DECREF(key);
+                       if (status < 0)
                                goto Fail;
-                       break;
                }
-               status = PyObject_SetItem(d, key, value);
-               Py_DECREF(key);
-               if (status < 0)
-                       goto Fail;
        }
 
+       if (PyErr_Occurred())
+               goto Fail;
        Py_DECREF(it);
        return d;