From b67f6e27e11264876e185cacd8ebabbf41c27fb0 Mon Sep 17 00:00:00 2001 From: Terry Jan Reedy Date: Wed, 10 Dec 2014 18:38:19 -0500 Subject: Issue #23006: Improve the documentation and indexing of dict.__missing__. Add an entry in the language datamodel special methods section. Revise and index its discussion in the stdtypes mapping/dict section. --- Doc/library/stdtypes.rst | 13 ++++++++----- Doc/reference/datamodel.rst | 6 ++++++ Misc/NEWS | 4 ++++ 3 files changed, 18 insertions(+), 5 deletions(-) diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst index 3f09b19..e076cbb 100644 --- a/Doc/library/stdtypes.rst +++ b/Doc/library/stdtypes.rst @@ -3761,11 +3761,13 @@ pairs within braces, for example: ``{'jack': 4098, 'sjoerd': 4127}`` or ``{4098: Return the item of *d* with key *key*. Raises a :exc:`KeyError` if *key* is not in the map. - If a subclass of dict defines a method :meth:`__missing__`, if the key *key* + .. index:: __missing__() + + If a subclass of dict defines a method :meth:`__missing__` and *key* is not present, the ``d[key]`` operation calls that method with the key *key* as argument. The ``d[key]`` operation then returns or raises whatever is - returned or raised by the ``__missing__(key)`` call if the key is not - present. No other operations or methods invoke :meth:`__missing__`. If + returned or raised by the ``__missing__(key)`` call. + No other operations or methods invoke :meth:`__missing__`. If :meth:`__missing__` is not defined, :exc:`KeyError` is raised. :meth:`__missing__` must be a method; it cannot be an instance variable:: @@ -3779,8 +3781,9 @@ pairs within braces, for example: ``{'jack': 4098, 'sjoerd': 4127}`` or ``{4098: >>> c['red'] 1 - See :class:`collections.Counter` for a complete implementation including - other methods helpful for accumulating and managing tallies. + The example above shows part of the implementation of + :class:`collections.Counter`. A different ``__missing__`` method is used + by :class:`collections.defaultdict`. .. describe:: d[key] = value diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index 618c257..d0eede7 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -1904,6 +1904,12 @@ through the container; for mappings, :meth:`__iter__` should be the same as indexes to allow proper detection of the end of the sequence. +.. method:: object.__missing__(self, key) + + Called by :class:`dict`\ .\ :meth:`__getitem__` to implement ``self[key]`` for dict subclasses + when key is not in the dictionary. + + .. method:: object.__setitem__(self, key, value) Called to implement assignment to ``self[key]``. Same note as for diff --git a/Misc/NEWS b/Misc/NEWS index d4cd62e..8a6fd24 100644 --- a/Misc/NEWS +++ b/Misc/NEWS @@ -9474,6 +9474,10 @@ C-API Documentation ------------- +- Issue #23006: Improve the documentation and indexing of dict.__missing__. + Add an entry in the language datamodel special methods section. + Revise and index its discussion in the stdtypes mapping/dict section. + - Issue #13989: Document that GzipFile does not support text mode, and give a more helpful error message when opened with an invalid mode string. -- cgit v0.12