nick.coghlan
2008-08-18 13:18:16 UTC
Author: nick.coghlan
Date: Mon Aug 18 15:18:16 2008
New Revision: 65811
Log:
Merged revisions 65810 via svnmerge from
svn+ssh://pythondev at 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
........
Modified:
python/branches/py3k/ (props changed)
python/branches/py3k/Doc/c-api/object.rst
python/branches/py3k/Doc/c-api/typeobj.rst
Modified: python/branches/py3k/Doc/c-api/object.rst
==============================================================================
--- python/branches/py3k/Doc/c-api/object.rst (original)
+++ python/branches/py3k/Doc/c-api/object.rst Mon Aug 18 15:18:16 2008
@@ -257,6 +257,16 @@
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.
Modified: python/branches/py3k/Doc/c-api/typeobj.rst
==============================================================================
--- python/branches/py3k/Doc/c-api/typeobj.rst (original)
+++ python/branches/py3k/Doc/c-api/typeobj.rst Mon Aug 18 15:18:16 2008
@@ -321,6 +321,14 @@
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.
Date: Mon Aug 18 15:18:16 2008
New Revision: 65811
Log:
Merged revisions 65810 via svnmerge from
svn+ssh://pythondev at 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
........
Modified:
python/branches/py3k/ (props changed)
python/branches/py3k/Doc/c-api/object.rst
python/branches/py3k/Doc/c-api/typeobj.rst
Modified: python/branches/py3k/Doc/c-api/object.rst
==============================================================================
--- python/branches/py3k/Doc/c-api/object.rst (original)
+++ python/branches/py3k/Doc/c-api/object.rst Mon Aug 18 15:18:16 2008
@@ -257,6 +257,16 @@
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.
Modified: python/branches/py3k/Doc/c-api/typeobj.rst
==============================================================================
--- python/branches/py3k/Doc/c-api/typeobj.rst (original)
+++ python/branches/py3k/Doc/c-api/typeobj.rst Mon Aug 18 15:18:16 2008
@@ -321,6 +321,14 @@
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.