https://github.com/python/cpython/commit/798f791dafb9cc5109ac19b086e98cfa6b943cfd
commit: 798f791dafb9cc5109ac19b086e98cfa6b943cfd
branch: main
author: Raymond Hettinger <[email protected]>
committer: rhettinger <[email protected]>
date: 2025-07-09T10:23:46-07:00
summary:
Minor edit: Move comments closer to the code they describe (gh-136477)
files:
M Lib/random.py
diff --git a/Lib/random.py b/Lib/random.py
index 86d562f0b8aaf6..c89cbb755abac8 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -844,8 +844,8 @@ def binomialvariate(self, n=1, p=0.5):
# BTRS: Transformed rejection with squeeze method by Wolfgang Hörmann
#
https://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.47.8407&rep=rep1&type=pdf
assert n*p >= 10.0 and p <= 0.5
- setup_complete = False
+ setup_complete = False
spq = _sqrt(n * p * (1.0 - p)) # Standard deviation of the
distribution
b = 1.15 + 2.53 * spq
a = -0.0873 + 0.0248 * b + 0.01 * p
@@ -860,22 +860,23 @@ def binomialvariate(self, n=1, p=0.5):
k = _floor((2.0 * a / us + b) * u + c)
if k < 0 or k > n:
continue
+ v = random()
# The early-out "squeeze" test substantially reduces
# the number of acceptance condition evaluations.
- v = random()
if us >= 0.07 and v <= vr:
return k
- # Acceptance-rejection test.
- # Note, the original paper erroneously omits the call to log(v)
- # when comparing to the log of the rescaled binomial distribution.
if not setup_complete:
alpha = (2.83 + 5.1 / b) * spq
lpq = _log(p / (1.0 - p))
m = _floor((n + 1) * p) # Mode of the distribution
h = _lgamma(m + 1) + _lgamma(n - m + 1)
setup_complete = True # Only needs to be done once
+
+ # Acceptance-rejection test.
+ # Note, the original paper erroneously omits the call to log(v)
+ # when comparing to the log of the rescaled binomial distribution.
v *= alpha / (a / (us * us) + b)
if _log(v) <= h - _lgamma(k + 1) - _lgamma(n - k + 1) + (k - m) *
lpq:
return k
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