commit f643b9a9c79928c4ca28d895e7e9a1dcf827cf00
author Raymond Hettinger <python@rcn.com> Sun May 25 22:13:41 2014 -0700
committer Raymond Hettinger <python@rcn.com> Sun May 25 22:13:41 2014 -0700
tree 52e182eb59f1caf8b7b59e3812ebcae56d70350d
parent 92df7529cb6c863d0fcd3247829b24833f62e285

Issue 8743:  Improve interoperability between sets and the collections.Set abstract base class.

Objects/setobject.c

diff --git a/Objects/setobject.c b/Objects/setobject.c
index db5cee2..b4b1178 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -1796,12 +1796,8 @@
     PyObject *r1, *r2;
 
     if(!PyAnySet_Check(w)) {
-        if (op == Py_EQ)
-            Py_RETURN_FALSE;
-        if (op == Py_NE)
-            Py_RETURN_TRUE;
-        PyErr_SetString(PyExc_TypeError, "can only compare to a set");
-        return NULL;
+        Py_INCREF(Py_NotImplemented);
+        return Py_NotImplemented;
     }
     switch (op) {
     case Py_EQ: