From: Raymond Hettinger <rhettinger@users.noreply.github.com>
Date: Fri, 20 May 2022 23:02:33 +0000 (-0500)
Subject: Take advantage of math.comb() in the nth_combination() recipe (#93027)
X-Git-Tag: v3.12.0a1~1476
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=59719a242d2191802476f5065236665379e226ac;p=thirdparty%2FPython%2Fcpython.git

Take advantage of math.comb() in the nth_combination() recipe (#93027)
---

diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 26c9253cb7f5..416c4eca5eb4 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -992,12 +992,7 @@ which incur interpreter overhead.
        "Equivalent to list(combinations(iterable, r))[index]"
        pool = tuple(iterable)
        n = len(pool)
-       if r < 0 or r > n:
-           raise ValueError
-       c = 1
-       k = min(r, n-r)
-       for i in range(1, k+1):
-           c = c * (n - k + i) // i
+       c = math.comb(n, r)
        if index < 0:
            index += c
        if index < 0 or index >= c:
@@ -1071,6 +1066,7 @@ which incur interpreter overhead.
 
     >>> import operator
     >>> import collections
+    >>> import math
 
     >>> take(10, count())
     [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]