[Python-checkins] Move random selection recipes from itertools.rst to random.rst (GH-98369)
miss-islington
webhook-mailer at python.org
Mon Oct 17 18:38:30 EDT 2022
https://github.com/python/cpython/commit/9cb30bb339fedf76cb7c3950114bb07c5d35efeb
commit: 9cb30bb339fedf76cb7c3950114bb07c5d35efeb
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: 2022-10-17T15:38:22-07:00
summary:
Move random selection recipes from itertools.rst to random.rst (GH-98369)
(cherry picked from commit 70732d8a4c98cdf3cc9efa5241ce33fb9bc323ca)
Co-authored-by: Raymond Hettinger <rhettinger at users.noreply.github.com>
files:
M Doc/library/itertools.rst
M Doc/library/random.rst
diff --git a/Doc/library/itertools.rst b/Doc/library/itertools.rst
index 49fb8407890c..26ede4b49a01 100644
--- a/Doc/library/itertools.rst
+++ b/Doc/library/itertools.rst
@@ -1000,31 +1000,6 @@ which incur interpreter overhead.
# first_true([a,b], x, f) --> a if f(a) else b if f(b) else x
return next(filter(pred, iterable), default)
- def random_product(*args, repeat=1):
- "Random selection from itertools.product(*args, **kwds)"
- pools = [tuple(pool) for pool in args] * repeat
- return tuple(map(random.choice, pools))
-
- def random_permutation(iterable, r=None):
- "Random selection from itertools.permutations(iterable, r)"
- pool = tuple(iterable)
- r = len(pool) if r is None else r
- return tuple(random.sample(pool, r))
-
- def random_combination(iterable, r):
- "Random selection from itertools.combinations(iterable, r)"
- pool = tuple(iterable)
- n = len(pool)
- indices = sorted(random.sample(range(n), r))
- return tuple(pool[i] for i in indices)
-
- def random_combination_with_replacement(iterable, r):
- "Random selection from itertools.combinations_with_replacement(iterable, r)"
- pool = tuple(iterable)
- n = len(pool)
- indices = sorted(random.choices(range(n), k=r))
- return tuple(pool[i] for i in indices)
-
def nth_combination(iterable, r, index):
"Equivalent to list(combinations(iterable, r))[index]"
pool = tuple(iterable)
diff --git a/Doc/library/random.rst b/Doc/library/random.rst
index 94215daad112..2b87a36f7c52 100644
--- a/Doc/library/random.rst
+++ b/Doc/library/random.rst
@@ -564,6 +564,37 @@ Simulation of arrival times and service deliveries for a multiserver queue::
Recipes
-------
+These recipes show how to efficiently make random selections
+from the combinatoric iterators in the :mod:`itertools` module:
+
+.. testcode::
+ import random
+
+ def random_product(*args, repeat=1):
+ "Random selection from itertools.product(*args, **kwds)"
+ pools = [tuple(pool) for pool in args] * repeat
+ return tuple(map(random.choice, pools))
+
+ def random_permutation(iterable, r=None):
+ "Random selection from itertools.permutations(iterable, r)"
+ pool = tuple(iterable)
+ r = len(pool) if r is None else r
+ return tuple(random.sample(pool, r))
+
+ def random_combination(iterable, r):
+ "Random selection from itertools.combinations(iterable, r)"
+ pool = tuple(iterable)
+ n = len(pool)
+ indices = sorted(random.sample(range(n), r))
+ return tuple(pool[i] for i in indices)
+
+ def random_combination_with_replacement(iterable, r):
+ "Random selection from itertools.combinations_with_replacement(iterable, r)"
+ pool = tuple(iterable)
+ n = len(pool)
+ indices = sorted(random.choices(range(n), k=r))
+ return tuple(pool[i] for i in indices)
+
The default :func:`.random` returns multiples of 2⁻⁵³ in the range
*0.0 ≤ x < 1.0*. All such numbers are evenly spaced and are exactly
representable as Python floats. However, many other representable
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