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bpo-40325: Deprecate set object support in random.sample() (GH-19591)

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Raymond Hettinger 2020-04-19 00:36:42 -07:00 • committed by GitHub
parent 482259d0dc
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4 changed files with 17 additions and 2 deletions
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7
Doc/library/random.rst
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@ -230,6 +230,13 @@ Functions for sequences
If the sample size is larger than the population size, a :exc:`ValueError` If the sample size is larger than the population size, a :exc:`ValueError`
is raised. is raised.
.. deprecated:: 3.9
In the future, the *population* must be a sequence. Instances of
:class:`set` are no longer supported. The set must first be converted
to a :class:`list` or :class:`tuple`, preferably in a deterministic
order so that the sample is reproducible.
Real-valued distributions Real-valued distributions
------------------------- -------------------------

5
Lib/random.py
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@ -367,9 +367,12 @@ class Random(_random.Random):
# causing them to eat more entropy than necessary. # causing them to eat more entropy than necessary.
if isinstance(population, _Set): if isinstance(population, _Set):
_warn('Sampling from a set deprecated\n'
'since Python 3.9 and will be removed in a subsequent version.',
DeprecationWarning, 2)
population = tuple(population) population = tuple(population)
if not isinstance(population, _Sequence): if not isinstance(population, _Sequence):
raise TypeError("Population must be a sequence or set. For dicts, use list(d).") raise TypeError("Population must be a sequence. For dicts or sets, use sorted(d).")
randbelow = self._randbelow randbelow = self._randbelow
n = len(population) n = len(population)
if not 0 <= k <= n: if not 0 <= k <= n:

6
Lib/test/test_random.py
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@ -147,7 +147,6 @@ class TestBasicOps:
def test_sample_inputs(self): def test_sample_inputs(self):
# SF bug #801342 -- population can be any iterable defining __len__() # SF bug #801342 -- population can be any iterable defining __len__()
self.gen.sample(set(range(20)), 2)
self.gen.sample(range(20), 2) self.gen.sample(range(20), 2)
self.gen.sample(range(20), 2) self.gen.sample(range(20), 2)
self.gen.sample(str('abcdefghijklmnopqrst'), 2) self.gen.sample(str('abcdefghijklmnopqrst'), 2)
@ -156,6 +155,11 @@ class TestBasicOps:
def test_sample_on_dicts(self): def test_sample_on_dicts(self):
self.assertRaises(TypeError, self.gen.sample, dict.fromkeys('abcdef'), 2) self.assertRaises(TypeError, self.gen.sample, dict.fromkeys('abcdef'), 2)
def test_sample_on_sets(self):
with self.assertWarns(DeprecationWarning):
population = {10, 20, 30, 40, 50, 60, 70}
self.gen.sample(population, k=5)
def test_choices(self): def test_choices(self):
choices = self.gen.choices choices = self.gen.choices
data = ['red', 'green', 'blue', 'yellow'] data = ['red', 'green', 'blue', 'yellow']

1
Misc/NEWS.d/next/Library/2020-04-18-19-40-00.bpo-40325.KWSvix.rst Normal file
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@ -0,0 +1 @@
Deprecated support for set objects in random.sample().