* Add unittests for iterators that report their length

* Document the differences between them
* Fix corner cases covered by the unittests
* Use Py_RETURN_NONE where possible for dictionaries

1 files changed, 10 insertions, 2 deletions

diff --git a/Objects/iterobject.c b/Objects/iterobject.c
index a407dd597f..25e4e11154 100644
--- a/Objects/iterobject.c
+++ b/Objects/iterobject.c
@@ -74,8 +74,16 @@ iter_iternext(PyObject *iterator)
 static int
 iter_len(seqiterobject *it)
 {
-	if (it->it_seq)
-		return PyObject_Size(it->it_seq) - it->it_index;
+	int seqsize, len;
+
+	if (it->it_seq) {
+		seqsize = PySequence_Size(it->it_seq);
+		if (seqsize == -1)
+			return -1;
+		len = seqsize - it->it_index;
+		if (len >= 0)
+			return len;
+	}
 	return 0;
 }