Index: Objects/rangeobject.c
===================================================================
--- Objects/rangeobject.c	(revision 56752)
+++ Objects/rangeobject.c	(working copy)
@@ -282,12 +282,69 @@
     return result;
 }
 
+static int
+range_contains(rangeobject *r, PyObject *ob) {
+    if (PyNumber_Check(ob)) {
+        int cmp_call, cmp_result;
+        PyObject *zero = PyLong_FromLong(0);
+
+        if (zero == NULL)
+            return 0;
+        cmp_call = PyObject_Cmp(r->step, zero, &cmp_result);
+        Py_CLEAR(zero);
+        if (cmp_call == -1)
+            return 0;
+        
+        int cmp_call1, cmp_result1;
+        int cmp_call2, cmp_result2;
+
+        assert(cmp_result != 0);
+        if (cmp_result > 0) { // positive steps
+            cmp_call1 = PyObject_Cmp(ob, r->start, &cmp_result1);
+            cmp_call2 = PyObject_Cmp(r->stop, ob, &cmp_result2);
+        }
+        else { // negative steps
+            cmp_call1 = PyObject_Cmp(r->start, ob, &cmp_result1);
+            cmp_call2 = PyObject_Cmp(ob, r->stop, &cmp_result2);
+        }
+        
+        if (cmp_call1 == -1 || cmp_call2 == -1) 
+            return 0;
+
+        if (cmp_result1 < 0 || cmp_result2 <= 0)
+            return 0;
+
+        PyObject *tmp1, *tmp2;
+        int result = 0;
+        
+        if ((tmp1 = PyNumber_Subtract(ob, r->start)) == NULL)
+            return 0;
+
+        if ((tmp2 = PyNumber_Remainder(tmp1, r->step)) == NULL)
+            return 0;
+
+        zero = PyLong_FromLong(0);
+        Py_INCREF(zero);
+        if (PyObject_Cmp(tmp2, zero, &result) == -1) {
+            Py_DECREF(zero);
+            return 0;
+        }
+        Py_CLEAR(zero);
+
+        return result == 0;
+    }
+    return 0;  
+}
+
 static PySequenceMethods range_as_sequence = {
     (lenfunc)range_length,	/* sq_length */
     0,			/* sq_concat */
     0,			/* sq_repeat */
     (ssizeargfunc)range_item, /* sq_item */
     0,			/* sq_slice */
+    0, /* sq_ass_item */
+    0, /* sq_ass_slice */
+    (objobjproc)range_contains, /* sq_contains */
 };
 
 static PyObject * range_iter(PyObject *seq);