[Python-checkins] Simplify sieve() recipe. Add edge case tests. (GH-96892)
miss-islington
webhook-mailer at python.org
Sat Sep 17 23:11:34 EDT 2022
https://github.com/python/cpython/commit/1448e2a42bf8bc53e486427d4515bce20b387d02
commit: 1448e2a42bf8bc53e486427d4515bce20b387d02
branch: 3.11
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: miss-islington <31488909+miss-islington at users.noreply.github.com>
date: 2022-09-17T20:11:29-07:00
summary:
Simplify sieve() recipe. Add edge case tests. (GH-96892)
(cherry picked from commit 78359b1d45608439f8e03b8e86174fe7b04d3e08)
Co-authored-by: Raymond Hettinger <rhettinger at users.noreply.github.com>
files:
M Doc/library/itertools.rst
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 41aff25d1f7..13fb80a2915 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -818,7 +818,7 @@ which incur interpreter overhead.
data = bytearray([1]) * n
data[:2] = 0, 0
limit = math.isqrt(n) + 1
- for p in compress(count(), islice(data, limit)):
+ for p in compress(range(limit), data):
data[p+p : n : p] = bytearray(len(range(p+p, n, p)))
return compress(count(), data)
@@ -1168,6 +1168,9 @@ which incur interpreter overhead.
>>> list(sieve(30))
[2, 3, 5, 7, 11, 13, 17, 19, 23, 29]
+ >>> small_primes = [2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59]
+ >>> all(list(sieve(n)) == [p for p in small_primes if p < n] for n in range(60))
+ True
>>> len(list(sieve(100)))
25
>>> len(list(sieve(1_000)))
@@ -1178,6 +1181,9 @@ which incur interpreter overhead.
9592
>>> len(list(sieve(1_000_000)))
78498
+ >>> carmichael = {561, 1105, 1729, 2465, 2821, 6601, 8911} # https://oeis.org/A002997
+ >>> set(sieve(10_000)).isdisjoint(carmichael)
+ True
>>> list(flatten([('a', 'b'), (), ('c', 'd', 'e'), ('f',), ('g', 'h', 'i')]))
['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i']
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