https://github.com/python/cpython/commit/4f0cfe53cbb56c32b097f9c38d66444960b5f17f
commit: 4f0cfe53cbb56c32b097f9c38d66444960b5f17f
branch: main
author: lighting9999 <[email protected]>
committer: rhettinger <[email protected]>
date: 2026-05-02T07:55:43-05:00
summary:
gh-149221:Fix binomialvariate Function for random module (gh-149222)
files:
A Misc/NEWS.d/next/Library/2026-05-02-01-09-29.gh-issue-149221.__KOks.rst
M Lib/random.py
M Lib/test/test_random.py
diff --git a/Lib/random.py b/Lib/random.py
index c89cbb755abac8..dc037629bab0db 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -836,7 +836,12 @@ def binomialvariate(self, n=1, p=0.5):
if not c:
return x
while True:
- y += _floor(_log2(random()) / c) + 1
+ try:
+ y += _floor(_log2(random()) / c) + 1
+ # The random() function can return 0.0, which causes log2(0.0)
to raise a ValueError.
+ # See https://github.com/python/cpython/issue/149221
+ except ValueError:
+ continue
if y > n:
return x
x += 1
diff --git a/Lib/test/test_random.py b/Lib/test/test_random.py
index 1e57b9244b4fd5..dbd3b855f536a0 100644
--- a/Lib/test/test_random.py
+++ b/Lib/test/test_random.py
@@ -1075,6 +1075,12 @@ def test_avg_std(self):
msg='%s%r' % (variate.__name__, args))
self.assertAlmostEqual(s2/(N-1), sigmasqrd, places=2,
msg='%s%r' % (variate.__name__, args))
+ def test_binomialvariate_log_zero(self):
+ # gh-149222: Variety random() return 0.0 no input Error
+ with unittest.mock.patch.object(random.Random, 'random', side_effect=
[0.0] + [0.5] * 20):
+ result = random.binomialvariate(10, 0.5)
+ self.assertIsInstance(result, int)
+ self.assertIn(result, range(11))
def test_constant(self):
g = random.Random()
diff --git
a/Misc/NEWS.d/next/Library/2026-05-02-01-09-29.gh-issue-149221.__KOks.rst
b/Misc/NEWS.d/next/Library/2026-05-02-01-09-29.gh-issue-149221.__KOks.rst
new file mode 100644
index 00000000000000..fab2b0f6a23489
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-05-02-01-09-29.gh-issue-149221.__KOks.rst
@@ -0,0 +1 @@
+Catch rare math domain error for :func:`random.binomialvariate`.
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