Improve algorithm for set.difference when the input is not a set.

diff --git a/Objects/setobject.c b/Objects/setobject.c
index 36072cef2c7929c9cde4cfbea59692657445e75d..4fbb645458f21ed5c091b64f22d7c4c46eecd377 100644 (file)
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -356,49 +356,6 @@ set_iand(PySetObject *so, PyObject *other)
        return (PyObject *)so;
 }
 
-static PyObject *
-set_difference(PySetObject *so, PyObject *other)
-{
-       PySetObject *result, *otherset=NULL;
-       PyObject *otherdata, *tgtdata;
-       PyObject *key, *value;
-       int pos = 0;
-
-       result = (PySetObject *)make_new_set(so->ob_type, NULL);
-       if (result == NULL)
-               return NULL;
-       tgtdata = result->data;
-
-       if (PyDict_Check(other))
-               otherdata = other;
-       else if (PyAnySet_Check(other))
-               otherdata = ((PySetObject *)other)->data;
-       else {
-               otherset = (PySetObject *)make_new_set(so->ob_type, other);
-               if (otherset == NULL) {
-                       Py_DECREF(result);
-                       return NULL;
-               }
-               otherdata = otherset->data;
-       }       
-
-       while (PyDict_Next(so->data, &pos, &key, &value)) {
-               if (!PyDict_Contains(otherdata, key)) {
-                       if (PyDict_SetItem(tgtdata, key, Py_True) == -1) {
-                               Py_XDECREF(otherset);
-                               return NULL;
-                       }
-               }
-       }
-       Py_XDECREF(otherset);
-       return (PyObject *)result;
-}
-
-PyDoc_STRVAR(difference_doc,
-"Return the difference of two sets as a new set.\n\
-\n\
-(i.e. all elements that are in this set but not the other.)");
-
 static PyObject *
 set_difference_update(PySetObject *so, PyObject *other)
 {
@@ -430,6 +387,49 @@ set_difference_update(PySetObject *so, PyObject *other)
 PyDoc_STRVAR(difference_update_doc,
 "Remove all elements of another set from this set.");
 
+static PyObject *
+set_difference(PySetObject *so, PyObject *other)
+{
+       PyObject *result, *tmp;
+       PyObject *otherdata, *tgtdata;
+       PyObject *key, *value;
+       int pos = 0;
+
+       if (PyDict_Check(other))
+               otherdata = other;
+       else if (PyAnySet_Check(other))
+               otherdata = ((PySetObject *)other)->data;
+       else {
+               result = set_copy(so);
+               if (result == NULL)
+                       return result;
+               tmp = set_difference_update((PySetObject *)result, other);
+               if (tmp != NULL) {
+                       Py_DECREF(tmp);
+                       return result;
+               }
+               Py_DECREF(result);
+               return NULL;
+       }
+       
+       result = make_new_set(so->ob_type, NULL);
+       if (result == NULL)
+               return NULL;
+       tgtdata = ((PySetObject *)result)->data;
+
+       while (PyDict_Next(so->data, &pos, &key, &value)) {
+               if (!PyDict_Contains(otherdata, key)) {
+                       if (PyDict_SetItem(tgtdata, key, Py_True) == -1)
+                               return NULL;
+               }
+       }
+       return result;
+}
+
+PyDoc_STRVAR(difference_doc,
+"Return the difference of two sets as a new set.\n\
+\n\
+(i.e. all elements that are in this set but not the other.)");
 static PyObject *
 set_sub(PySetObject *so, PyObject *other)
 {