[Python-checkins] Take advantage of math.comb() in the nth_combination() recipe (#93027)
rhettinger
webhook-mailer at python.org
Fri May 20 19:02:37 EDT 2022
https://github.com/python/cpython/commit/59719a242d2191802476f5065236665379e226ac
commit: 59719a242d2191802476f5065236665379e226ac
branch: main
author: Raymond Hettinger <rhettinger at users.noreply.github.com>
committer: rhettinger <rhettinger at users.noreply.github.com>
date: 2022-05-20T18:02:33-05:00
summary:
Take advantage of math.comb() in the nth_combination() recipe (#93027)
files:
M Doc/library/itertools.rst
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 26c9253cb7f5f..416c4eca5eb48 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]
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