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gh-157840: Special-case member descriptors when using hasattr #157866

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Merged
ZeroIntensity merged 5 commits into from
Sep 20, 2026
Merged

gh-157840: Special-case member descriptors when using hasattr #157866

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086cb91
Improve performance for hasattr() with unassigned slots.
ZeroIntensity Sep 20, 2026
74c0828
Add blurb.
ZeroIntensity Sep 20, 2026
cc752b9
Simplify comment.
ZeroIntensity Sep 20, 2026
9878c2b
Adjust formatting.
ZeroIntensity Sep 20, 2026
8e74138
Mention getattr() in the blurb.
ZeroIntensity Sep 20, 2026
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Core_and_Builtins/2026-09-20-12-11-01.gh-issue-157840.EAo1Kp.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Speed up calls to :func:`hasattr` and three-argument :func:`getattr` for
unassigned attributes in an object's :attr:`~object.__slots__` by roughly 6x.
13 changes: 13 additions & 0 deletions Objects/object.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1924,6 +1924,19 @@ _PyObject_GenericGetAttrWithDict(PyObject *obj, PyObject *name,
if (descr != NULL) {
f = Py_TYPE(descr)->tp_descr_get;
if (f != NULL && PyDescr_IsData(descr)) {
// gh-157840: We special-case member descriptors here to avoid
// allocating an extra AttributeError
if (suppress && Py_IS_TYPE(descr, &PyMemberDescr_Type)) {
PyMemberDef *member = ((PyMemberDescrObject *)descr)->d_member;
if (member->type == Py_T_OBJECT_EX
&& !(member->flags & Py_AUDIT_READ)
&& PyObject_TypeCheck(obj, PyDescr_TYPE(descr))) {
PyObject **addr = _PyMember_GetOffset(obj, member);
if (FT_ATOMIC_LOAD_PTR(*addr) == NULL) {
goto done;
}
}
}
res = f(descr, obj, (PyObject *)Py_TYPE(obj));
if (res == NULL && suppress &&
PyErr_ExceptionMatches(PyExc_AttributeError)) {
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