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gh-135385: Do not reserve inline values for attributes stored in slots #156656

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gh-135385: Do not reserve inline values for attributes stored in slots #156656

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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-08-30-16-30-00.gh-issue-135385.Wn7Rd4.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,3 @@
Reduce the memory consumption of instances of classes which define
``__slots__`` and also have a ``__dict__``. Space for the attributes stored
in slots is no longer reserved in the inline values of every instance.
5 changes: 5 additions & 0 deletions Objects/dictobject.c
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Expand Up @@ -7286,6 +7286,11 @@ _PyDict_NewKeysForClass(PyHeapTypeObject *cls)
PyObject *key = PyTuple_GET_ITEM(attrs, i);
Py_hash_t hash;
if (PyUnicode_CheckExact(key) && (hash = unicode_get_hash(key)) != -1) {
/* An attribute stored in a slot never uses the dict. */
PyObject *descr = _PyType_Lookup((PyTypeObject *)cls, key);
if (descr != NULL && Py_IS_TYPE(descr, &PyMemberDescr_Type)) {
continue;
}
if (insert_split_key(keys, key, hash) == DKIX_EMPTY) {
break;
}
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