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Move random selection recipes from itertools.rst to random.rst (GH-98369)

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(cherry picked from commit 70732d8a4c)

Co-authored-by: Raymond Hettinger <rhettinger@users.noreply.github.com>
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Miss Islington (bot) 2022-10-17 15:38:22 -07:00 • committed by GitHub
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2 changed files with 31 additions and 25 deletions
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25
Doc/library/itertools.rst
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@ -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 # first_true([a,b], x, f) --> a if f(a) else b if f(b) else x
return next(filter(pred, iterable), default) 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): def nth_combination(iterable, r, index):
"Equivalent to list(combinations(iterable, r))[index]" "Equivalent to list(combinations(iterable, r))[index]"
pool = tuple(iterable) pool = tuple(iterable)

31
Doc/library/random.rst
View file

@ -564,6 +564,37 @@ Simulation of arrival times and service deliveries for a multiserver queue::
Recipes 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 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 *0.0 ≤ x < 1.0*. All such numbers are evenly spaced and are exactly
representable as Python floats. However, many other representable representable as Python floats. However, many other representable