[Python-checkins] bpo-35020: Link to sorting examples from list.sort() (GH-9931)

Raymond Hettinger webhook-mailer at python.org
Sat Oct 20 17:39:06 EDT 2018

commit: 890a4b92933be8e7c554222d99ef829c88fa8637
branch: master
author: Xtreak <tirkarthi at users.noreply.github.com>
committer: Raymond Hettinger <rhettinger at users.noreply.github.com>
date: 2018-10-20T14:39:03-07:00

bpo-35020: Link to sorting examples from list.sort() (GH-9931)

M Doc/howto/sorting.rst
M Doc/library/stdtypes.rst

diff --git a/Doc/howto/sorting.rst b/Doc/howto/sorting.rst
index 128044662899..b2fccb19f5d4 100644
--- a/Doc/howto/sorting.rst
+++ b/Doc/howto/sorting.rst
@@ -145,6 +145,17 @@ ascending *age*, do the *age* sort first and then sort again using *grade*:
     >>> sorted(s, key=attrgetter('grade'), reverse=True)       # now sort on primary key, descending
     [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
+This can be abstracted out into a wrapper function that can take a list and
+tuples of field and order to sort them on multiple passes.
+    >>> def multisort(xs, specs):
+    ...     for key, reverse in reversed(specs):
+    ...         xs.sort(key=attrgetter(key), reverse=reverse)
+    ...     return xs
+    >>> multisort(list(student_objects), (('grade', True), ('age', False)))
+    [('dave', 'B', 10), ('jane', 'B', 12), ('john', 'A', 15)]
 The `Timsort <https://en.wikipedia.org/wiki/Timsort>`_ algorithm used in Python
 does multiple sorts efficiently because it can take advantage of any ordering
 already present in a dataset.
@@ -246,7 +257,7 @@ To convert to a key function, just wrap the old comparison function:
 .. testsetup::
-    from functools import cmp_to_key
+    >>> from functools import cmp_to_key
 .. doctest::
diff --git a/Doc/library/stdtypes.rst b/Doc/library/stdtypes.rst
index d0d5c6157290..01fb5d5e15cd 100644
--- a/Doc/library/stdtypes.rst
+++ b/Doc/library/stdtypes.rst
@@ -1201,6 +1201,8 @@ application).
       --- this is helpful for sorting in multiple passes (for example, sort by
       department, then by salary grade).
+      For sorting examples and a brief sorting tutorial, see :ref:`sortinghowto`.
       .. impl-detail::
          While a list is being sorted, the effect of attempting to mutate, or even
@@ -4752,4 +4754,3 @@ types, where they are relevant.  Some of these are not reported by the
 .. [5] To format only a tuple you should therefore provide a singleton tuple whose only
    element is the tuple to be formatted.

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