diff options
| -rw-r--r-- | Lib/random.py | 6 | ||||
| -rw-r--r-- | Lib/test/test_random.py | 16 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Library/2025-02-21-10-32-05.gh-issue-130285.C0fkh7.rst | 4 |
3 files changed, 21 insertions, 5 deletions
diff --git a/Lib/random.py b/Lib/random.py index 8b9a270..1abcae7 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -421,11 +421,11 @@ class Random(_random.Random): cum_counts = list(_accumulate(counts)) if len(cum_counts) != n: raise ValueError('The number of counts does not match the population') - total = cum_counts.pop() + total = cum_counts.pop() if cum_counts else 0 if not isinstance(total, int): raise TypeError('Counts must be integers') - if total <= 0: - raise ValueError('Total of counts must be greater than zero') + if total < 0: + raise ValueError('Counts must be non-negative') selections = self.sample(range(total), k=k) bisect = _bisect return [population[bisect(cum_counts, s)] for s in selections] diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py index 51f9193..96f6cc8 100644 --- a/Lib/test/test_random.py +++ b/Lib/test/test_random.py @@ -226,14 +226,26 @@ class TestBasicOps: with self.assertRaises(ValueError): sample(['red', 'green', 'blue'], counts=[-3, -7, -8], k=2) # counts are negative with self.assertRaises(ValueError): - sample(['red', 'green', 'blue'], counts=[0, 0, 0], k=2) # counts are zero - with self.assertRaises(ValueError): sample(['red', 'green'], counts=[10, 10], k=21) # population too small with self.assertRaises(ValueError): sample(['red', 'green', 'blue'], counts=[1, 2], k=2) # too few counts with self.assertRaises(ValueError): sample(['red', 'green', 'blue'], counts=[1, 2, 3, 4], k=2) # too many counts + # Cases with zero counts match equivalents without counts (see gh-130285) + self.assertEqual( + sample('abc', k=0, counts=[0, 0, 0]), + sample([], k=0), + ) + self.assertEqual( + sample([], 0, counts=[]), + sample([], 0), + ) + with self.assertRaises(ValueError): + sample([], 1, counts=[]) + with self.assertRaises(ValueError): + sample('x', 1, counts=[0]) + def test_choices(self): choices = self.gen.choices data = ['red', 'green', 'blue', 'yellow'] diff --git a/Misc/NEWS.d/next/Library/2025-02-21-10-32-05.gh-issue-130285.C0fkh7.rst b/Misc/NEWS.d/next/Library/2025-02-21-10-32-05.gh-issue-130285.C0fkh7.rst new file mode 100644 index 0000000..7e0a4d2 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2025-02-21-10-32-05.gh-issue-130285.C0fkh7.rst @@ -0,0 +1,4 @@ +Fix corner case for :func:`random.sample` allowing the *counts* parameter to +specify an empty population. So now, ``sample([], 0, counts=[])`` and +``sample('abc', k=0, counts=[0, 0, 0])`` both give the same result as +``sample([], 0)``. |