On Sun, Apr 19, 2015 at 2:09 AM, Paul Moore <p.f.moore@gmail.com> wrote:

So I'm not clear what "small change" you're referring to here:

* A change to CPython to reduce the number of false positives by
making this case return False? If that, then no, I don't think a PEP
is needed. But note that user code still can't assume that the above
behaviour couldn't still happen in *other* cases, so the change would
be of limited value (and whether it gets accepted depends on whether
the complexity is justified by the benefit).
* A change to the definition of callable() to remove the possibility
of false positives at all? In that case, yes, a PEP probably *is*
needed, as that's going to affect an awful lot of corner cases, and
will impact all implementations. It's probably not correct to call
this a "small change".
* Something else?

​The discussion was about this small change:

 int
 PyCallable_Check(PyObject *x)
 {
-    if (x == NULL)
+    if (x == NULL) {
         return 0;
-    return x->ob_type->tp_call != NULL;
+    }
+
+    return Py_TYPE(x)->tp_call && _PyObject_HasAttrId(x, &PyId___call__);
 }

There are more explanations in the thread in case you want to know more.

Thanks,
-- Ionel Cristian Mărieș, http://blog.ionelmc.ro