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Diffstat (limited to 'Doc/glossary.rst')
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diff --git a/Doc/glossary.rst b/Doc/glossary.rst index 24bbb37..161e52c 100644 --- a/Doc/glossary.rst +++ b/Doc/glossary.rst @@ -356,6 +356,26 @@ Glossary More information can be found in :ref:`typeiter`. + key function + A key function or collation function is a callable that returns a value + used for sorting or ordering. For example, :func:`locale.strxfrm` is + used to produce a sort key that is aware of locale specific sort + conventions. + + A number of tools in Python accept key functions to control how elements + are ordered or grouped. They include :func:`min`, :func:`max`, + :func:`sorted`, :meth:`list.sort`, :func:`heapq.nsmallest`, + :func:`heapq.nlargest`, and :func:`itertools.groupby`. + + There are several ways to create a key function. For example. the + :meth:`str.lower` method can serve as a key function for case insensitive + sorts. Alternatively, an ad-hoc key function can be built from a + :keyword:`lambda` expression such as ``lambda r: (r[0], r[2])``. Also, + the :mod:`operator` module provides three key function constuctors: + :func:`~operator.attrgetter`, :func:`~operator.itemgetter`, and + :func:`~operator.methodcaller`. See the :ref:`Sorting HOW TO + <sortinghowto>` for examples of how to create and use key functions. + keyword argument Arguments which are preceded with a ``variable_name=`` in the call. The variable name designates the local name in the function to which the @@ -379,7 +399,7 @@ Glossary :keyword:`lambda` expression such as ``lambda r: (r[0], r[2])``. Also, the :mod:`operator` module provides three key function constuctors: :func:`~operator.attrgetter`, :func:`~operator.itemgetter`, and - :func:`~operator.methodcaller`. See the :ref:`sorting-howto` for + :func:`~operator.methodcaller`. See the :ref:`sortinghowto` for examples of how to create and use key functions. lambda |