From: Raymond Hettinger <rhettinger@users.noreply.github.com>
Date: Thu, 14 Dec 2023 23:27:39 +0000 (-0600)
Subject: Optimize unique_justseen() recipe for a common case. (gh-113147)
X-Git-Tag: v3.13.0a3~370
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=5f7d7353b47ccf634b9b65f933d3fdeeb395301f;p=thirdparty%2FPython%2Fcpython.git

Optimize unique_justseen() recipe for a common case. (gh-113147)
---

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 36cea9a835f3..03127afe1b44 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -1017,6 +1017,8 @@ which incur interpreter overhead.
        "List unique elements, preserving order. Remember only the element just seen."
        # unique_justseen('AAAABBBCCDAABBB') --> A B C D A B
        # unique_justseen('ABBcCAD', str.lower) --> A B c A D
+       if key is None:
+           return map(operator.itemgetter(0), groupby(iterable))
        return map(next, map(operator.itemgetter(1), groupby(iterable, key)))