From 7a70a3a6f4a8a010d85fabf5c479cf92296d8056 Mon Sep 17 00:00:00 2001 From: Nick Coghlan Date: Mon, 18 Aug 2008 13:18:16 +0000 Subject: Merged revisions 65810 via svnmerge from svn+ssh://pythondev@svn.python.org/python/trunk ........ r65810 | nick.coghlan | 2008-08-18 23:14:22 +1000 (Mon, 18 Aug 2008) | 1 line Issue 2235: document PyObject_HashNotImplemented ........ --- Doc/c-api/object.rst | 10 ++++++++++ Doc/c-api/typeobj.rst | 8 ++++++++ 2 files changed, 18 insertions(+) diff --git a/Doc/c-api/object.rst b/Doc/c-api/object.rst index f377c75..9851825 100644 --- a/Doc/c-api/object.rst +++ b/Doc/c-api/object.rst @@ -257,6 +257,16 @@ is considered sufficient for this determination. This is the equivalent of the Python expression ``hash(o)``. +.. cfunction:: long PyObject_HashNotImplemented(PyObject *o) + + Set a TypeError indicating that ``type(o)`` is not hashable and return ``-1``. + This function receives special treatment when stored in a ``tp_hash`` slot, + allowing a type to explicit indicate to the interpreter that it is not + hashable. + + .. versionadded:: 2.6 + + .. cfunction:: int PyObject_IsTrue(PyObject *o) Returns ``1`` if the object *o* is considered to be true, and ``0`` otherwise. diff --git a/Doc/c-api/typeobj.rst b/Doc/c-api/typeobj.rst index 8031c10..2b35aee 100644 --- a/Doc/c-api/typeobj.rst +++ b/Doc/c-api/typeobj.rst @@ -321,6 +321,14 @@ type objects) *must* have the :attr:`ob_size` field. error occurs during the computation of the hash value, the function should set an exception and return ``-1``. + This field can be set explicitly to :cfunc:`PyObject_HashNotImplemented` to + block inheritance of the hash method from a parent type. This is interpreted + as the equivalent of ``__hash__ = None`` at the Python level, causing + ``isinstance(o, collections.Hashable)`` to correctly return ``False``. Note + that the converse is also true - setting ``__hash__ = None`` on a class at + the Python level will result in the ``tp_hash`` slot being set to + :cfunc:`PyObject_HashNotImplemented`. + When this field is not set, two possibilities exist: if the :attr:`tp_compare` and :attr:`tp_richcompare` fields are both *NULL*, a default hash value based on the object's address is returned; otherwise, a :exc:`TypeError` is raised. -- cgit v0.12