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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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Improve performance for hasattr() with unassigned slots.
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@ZeroIntensity
ZeroIntensity committed Sep 20, 2026
commit 086cb91a043bf3ab89d02ddeeaf166418aa7aac6
16 changes: 16 additions & 0 deletions Objects/object.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1924,6 +1924,22 @@ _PyObject_GenericGetAttrWithDict(PyObject *obj, PyObject *name,
if (descr != NULL) {
f = Py_TYPE(descr)->tp_descr_get;
if (f != NULL && PyDescr_IsData(descr)) {
// gh-157840: When using hasattr(), slot members without assigned values
// need to go through __get__(), which involves creating an AttributeError
// object (which is really slow). There's no way to supply "suppress"
// to the tp_descr_get() function, so we just special-case member
// descriptors here to improve performance.

@serhiy-storchaka serhiy-storchaka Sep 20, 2026

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Could you please simplify the comment, leaving the substantial part?

@ZeroIntensity ZeroIntensity Sep 20, 2026

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Done

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) &&

@serhiy-storchaka serhiy-storchaka Sep 20, 2026

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Inconsistent formatting. && after and before line split.

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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