https://github.com/python/cpython/commit/64bccca752e62cc478a9d746f97169c55e24682b commit: 64bccca752e62cc478a9d746f97169c55e24682b branch: 3.14 author: Miss Islington (bot) <[email protected]> committer: serhiy-storchaka <[email protected]> date: 2026-07-19T08:42:20Z summary:
[3.14] gh-154001: Avoid division by zero in binomialvariate (GH-154004) (GH-154051) (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 726a71e782893c..0e6a183d179f48 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 0217ebd132b110..3739fe0ac393b3 100644 --- a/Lib/test/test_random.py +++ b/Lib/test/test_random.py @@ -1074,6 +1074,14 @@ def test_avg_std(self): self.assertAlmostEqual(s2/(N-1), sigmasqrd, places=2, msg='%s%r' % (variate.__name__, args)) + 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]
