From 1438b779971605e516bd0a4051a704d6ffbbd58d Mon Sep 17 00:00:00 2001 From: Petr Viktorin Date: Mon, 7 Nov 2022 19:45:50 +0100 Subject: gh-96746: Docs: Clear up Py_TPFLAGS_DISALLOW_INSTANTIATION inheritance (GH-99002) MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The flag is not inherited, but its effect -- a NULL tp_new -- is. Drop hints for people who come here wanting to “disallow instantiation”. --- Doc/c-api/typeobj.rst | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/Doc/c-api/typeobj.rst b/Doc/c-api/typeobj.rst index 8ccdece..4c462f4 100644 --- a/Doc/c-api/typeobj.rst +++ b/Doc/c-api/typeobj.rst @@ -1245,6 +1245,17 @@ and :c:type:`PyType_Type` effectively act as defaults.) **Inheritance:** This flag is not inherited. + However, subclasses will not be instantiable unless they provide a + non-NULL :c:member:`~PyTypeObject.tp_new` (which is only possible + via the C API). + + .. note:: + + To disallow instantiating a class directly but allow instantiating + its subclasses (e.g. for an :term:`abstract base class`), + do not use this flag. + Instead, make :c:member:`~PyTypeObject.tp_new` only succeed for + subclasses. .. versionadded:: 3.10 -- cgit v0.12