Issue 3689: list_reverseiterator should support __length_hint__ instead of __len__.

diff --git a/Lib/test/list_tests.py b/Lib/test/list_tests.py
index 6250908ba5616a9c91262485ff39ddb041a1dbaa..5b1aa75362a9d38c2fd6c150b88870ceaf13f8d3 100644 (file)
--- a/Lib/test/list_tests.py
+++ b/Lib/test/list_tests.py
@@ -93,6 +93,8 @@ class CommonTest(seq_tests.CommonTest):
         self.assertRaises(StopIteration, next, r)
         self.assertEqual(list(reversed(self.type2test())),
                          self.type2test())
+        # Bug 3689: make sure list-reversed-iterator doesn't have __len__
+        self.assertRaises(TypeError, len, reversed([1,2,3]))
 
     def test_setitem(self):
         a = self.type2test([0, 1])

diff --git a/Misc/NEWS b/Misc/NEWS
index a8565c9d49ef12d01040be70af62df954376b57a..b1bd08559c23ba97ffd7a6dfc2500144d0bda919 100644 (file)
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -16,6 +16,9 @@ Core and Builtins
   interpreter to abort ("Fatal Python error: Could not reset the stack!")
   instead of throwing a MemoryError.
 
+- Issue #3689: The list reversed iterator now supports __length_hint__
+  instead of __len__.  Behavior now matches other reversed iterators.
+
 - Issue #4367: Python would segfault during compiling when the unicodedata
   module couldn't be imported and \N escapes were present.
 

diff --git a/Objects/listobject.c b/Objects/listobject.c
index d5acec1f05105ddcfc52a2dd044c7183ca57fcca..40077a1b2b3686e733eb23638aab2b17b7ed727f 100644 (file)
--- a/Objects/listobject.c
+++ b/Objects/listobject.c
@@ -2736,11 +2736,11 @@ static PyObject *list_reversed(PyListObject *, PyObject *);
 static void listreviter_dealloc(listreviterobject *);
 static int listreviter_traverse(listreviterobject *, visitproc, void *);
 static PyObject *listreviter_next(listreviterobject *);
-static Py_ssize_t listreviter_len(listreviterobject *);
+static PyObject *listreviter_len(listreviterobject *);
 
-static PySequenceMethods listreviter_as_sequence = {
-       (lenfunc)listreviter_len,       /* sq_length */
-       0,                              /* sq_concat */
+static PyMethodDef listreviter_methods[] = {
+       {"__length_hint__", (PyCFunction)listreviter_len, METH_NOARGS, length_hint_doc},
+       {NULL,          NULL}           /* sentinel */
 };
 
 PyTypeObject PyListRevIter_Type = {
@@ -2756,7 +2756,7 @@ PyTypeObject PyListRevIter_Type = {
        0,                                      /* tp_compare */
        0,                                      /* tp_repr */
        0,                                      /* tp_as_number */
-       &listreviter_as_sequence,               /* tp_as_sequence */
+       0,                                      /* tp_as_sequence */
        0,                                      /* tp_as_mapping */
        0,                                      /* tp_hash */
        0,                                      /* tp_call */
@@ -2772,6 +2772,7 @@ PyTypeObject PyListRevIter_Type = {
        0,                                      /* tp_weaklistoffset */
        PyObject_SelfIter,                      /* tp_iter */
        (iternextfunc)listreviter_next,         /* tp_iternext */
+       listreviter_methods,            /* tp_methods */
        0,
 };
 
@@ -2827,12 +2828,12 @@ listreviter_next(listreviterobject *it)
        return NULL;
 }
 
-static Py_ssize_t
+static PyObject *
 listreviter_len(listreviterobject *it)
 {
        Py_ssize_t len = it->it_index + 1;
        if (it->it_seq == NULL || PyList_GET_SIZE(it->it_seq) < len)
-               return 0;
-       return len;
+               len = 0;
+       return PyLong_FromSsize_t(len);
 }