patch.diff

diff --git a/Objects/abstract.c b/Objects/abstract.c
index ee744de..1cabd94 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -1602,12 +1602,21 @@ PyNumber_Int(PyObject *o)
   const char *buffer;
 	Py_ssize_t buffer_len;
 
+	static PyObject *int_name = NULL;
+	PyObject *int_func;
+
 	if (trunc_name == NULL) {
 		trunc_name = PyString_InternFromString("__trunc__");
 		if (trunc_name == NULL)
 			return NULL;
 	}
 
+	if (int_name == NULL) {
+		int_name = PyString_InternFromString("__int__");
+		if (int_name == NULL)
+			return NULL;
+ 	}
+
 	if (o == NULL)
 		return null_error();
 	if (PyInt_CheckExact(o)) {
@@ -1615,9 +1624,10 @@ PyNumber_Int(PyObject *o)
 		return o;
 	}
 	m = o->ob_type->tp_as_number;
-	if (m && m->nb_int) { /* This should include subclasses of int */
+	int_func = PyObject_GetAttr(o, int_name);
+	if ((m && m->nb_int) || int_func) { /* This should include subclasses of int */
 		/* Classic classes always take this branch. */
-		PyObject *res = m->nb_int(o);
+		PyObject *res = int_func? PyEval_CallObject(int_func, NULL) : m->nb_int(o);
 		if (res && (!PyInt_Check(res) && !PyLong_Check(res))) {
 			PyErr_Format(PyExc_TypeError,
 				     "__int__ returned non-int (type %.200s)",

test.py

class Foo(object):
    def __int__(self):
        return 24
 
foo = Foo()
foo.__int__ = lambda: 42
print(int(foo))
 
 
# $ python test.py
# 24
 
# patched version
# $ ./python.exe test.py
# 42