https://github.com/python/cpython/commit/15335ae20f1f214a36148d31475a1de61614d4d6 commit: 15335ae20f1f214a36148d31475a1de61614d4d6 branch: 3.15 author: Miss Islington (bot) <[email protected]> committer: serhiy-storchaka <[email protected]> date: 2026-07-19T09:28:18Z summary:
[3.15] gh-154001: Avoid division by zero in binomialvariate (GH-154004) (GH-154050) (cherry picked from commit 1f1374009b681814642ca199136815b223fd90ae) Co-authored-by: Łukasz <[email protected]> files: A Misc/NEWS.d/next/Library/2026-07-18-17-09-49.gh-issue-154001.3brrUv.rst M Lib/random.py M Lib/test/test_random.py diff --git a/Lib/random.py b/Lib/random.py index 4541267bab866a..7db761034509d3 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -861,7 +861,11 @@ def binomialvariate(self, n=1, p=0.5): u = random() u -= 0.5 us = 0.5 - _fabs(u) - k = _floor((2.0 * a / us + b) * u + c) + try: + k = _floor((2.0 * a / us + b) * u + c) + except ZeroDivisionError: + # Reject case where random() returned 0.0 + continue if k < 0 or k > n: continue v = random() diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py index dbd3b855f536a0..8d093ab1b7014a 100644 --- a/Lib/test/test_random.py +++ b/Lib/test/test_random.py @@ -1082,6 +1082,14 @@ def test_binomialvariate_log_zero(self): self.assertIsInstance(result, int) self.assertIn(result, range(11)) + def test_binomialvariate_btrs_random_zero(self): + for p, expected in ((0.25, 25), (0.75, 75)): + with self.subTest(p=p): + g = random.Random() + with unittest.mock.patch.object( + g, 'random', side_effect=(0.0, 0.5, 0.5)): + self.assertEqual(g.binomialvariate(100, p), expected) + def test_constant(self): g = random.Random() N = 100 diff --git a/Misc/NEWS.d/next/Library/2026-07-18-17-09-49.gh-issue-154001.3brrUv.rst b/Misc/NEWS.d/next/Library/2026-07-18-17-09-49.gh-issue-154001.3brrUv.rst new file mode 100644 index 00000000000000..ff019aa3618847 --- /dev/null +++ b/Misc/NEWS.d/next/Library/2026-07-18-17-09-49.gh-issue-154001.3brrUv.rst @@ -0,0 +1,2 @@ +Fix :func:`random.binomialvariate` raising :exc:`ZeroDivisionError` +when :func:`random.random` returns zero. _______________________________________________ Python-checkins mailing list -- [email protected] To unsubscribe send an email to [email protected] https://mail.python.org/mailman3//lists/python-checkins.python.org Member address: [email protected]
