Issue #26194: Inserting into a full deque to raise an IndexError
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index e89da35..092221f 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -477,8 +477,8 @@
Insert *x* into the deque at position *i*.
- If the insertion causes a bounded deque to grow beyond *maxlen*, the
- rightmost element is then removed to restore the size limit.
+ If the insertion would cause a bounded deque to grow beyond *maxlen*,
+ an :exc:`IndexError` is raised.
.. versionadded:: 3.5
diff --git a/Lib/test/test_deque.py b/Lib/test/test_deque.py
index d2a4633..2ca508d 100644
--- a/Lib/test/test_deque.py
+++ b/Lib/test/test_deque.py
@@ -304,19 +304,20 @@
s.insert(i, 'Z')
self.assertEqual(list(d), s)
- def test_index_bug_26194(self):
+ def test_insert_bug_26194(self):
data = 'ABC'
- for i in range(len(data) + 1):
- d = deque(data, len(data))
- d.insert(i, None)
- s = list(data)
- s.insert(i, None)
- s.pop()
- self.assertEqual(list(d), s)
- if i < len(data):
- self.assertIsNone(d[i])
+ d = deque(data, maxlen=len(data))
+ with self.assertRaises(IndexError):
+ d.insert(2, None)
+
+ elements = 'ABCDEFGHI'
+ for i in range(-len(elements), len(elements)):
+ d = deque(elements, maxlen=len(elements)+1)
+ d.insert(i, 'Z')
+ if i >= 0:
+ self.assertEqual(d[i], 'Z')
else:
- self.assertTrue(None not in d)
+ self.assertEqual(d[i-1], 'Z')
def test_imul(self):
for n in (-10, -1, 0, 1, 2, 10, 1000):
diff --git a/Misc/NEWS b/Misc/NEWS
index a95d2a0..ba1f4de 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -22,8 +22,8 @@
compiler issues.
- Issue #26194: Deque.insert() gave odd results for bounded deques that had
- reached their maximum size. Now, the insert will happen normally and then
- any overflowing element will be truncated from the right side.
+ reached their maximum size. Now an IndexError will be raised when attempting
+ to insert into a full deque.
- Issue #25843: When compiling code, don't merge constants if they are equal
but have a different types. For example, ``f1, f2 = lambda: 1, lambda: 1.0``
diff --git a/Modules/_collectionsmodule.c b/Modules/_collectionsmodule.c
index b9c4f3b..10fbcfe 100644
--- a/Modules/_collectionsmodule.c
+++ b/Modules/_collectionsmodule.c
@@ -973,16 +973,13 @@
Py_ssize_t index;
Py_ssize_t n = Py_SIZE(deque);
PyObject *value;
- PyObject *oldvalue;
PyObject *rv;
if (!PyArg_ParseTuple(args, "nO:insert", &index, &value))
return NULL;
if (deque->maxlen == Py_SIZE(deque)) {
- if (index >= deque->maxlen || Py_SIZE(deque) == 0)
- Py_RETURN_NONE;
- oldvalue = deque_pop(deque, NULL);
- Py_DECREF(oldvalue);
+ PyErr_SetString(PyExc_IndexError, "deque already at its maximum size");
+ return NULL;
}
if (index >= n)
return deque_append(deque, value);