https://github.com/python/cpython/commit/e6893943b75c6b0ea54c2db99bdf1436f404a87a
commit: e6893943b75c6b0ea54c2db99bdf1436f404a87a
branch: main
author: Raymond Hettinger <[email protected]>
committer: rhettinger <[email protected]>
date: 2026-04-13T11:29:15-05:00
summary:
Minor improvement to statistics.pdf() (gh-148500)
files:
M Lib/statistics.py
diff --git a/Lib/statistics.py b/Lib/statistics.py
index 26cf925529ea60..e635b99f958e44 100644
--- a/Lib/statistics.py
+++ b/Lib/statistics.py
@@ -145,6 +145,7 @@
from collections import Counter, namedtuple, defaultdict
_SQRT2 = sqrt(2.0)
+_SQRT2PI = sqrt(tau)
_random = random
## Exceptions ##############################################################
@@ -1257,11 +1258,11 @@ def samples(self, n, *, seed=None):
def pdf(self, x):
"Probability density function. P(x <= X < x+dx) / dx"
- variance = self._sigma * self._sigma
- if not variance:
+ sigma = self._sigma
+ if not sigma:
raise StatisticsError('pdf() not defined when sigma is zero')
- diff = x - self._mu
- return exp(diff * diff / (-2.0 * variance)) / sqrt(tau * variance)
+ z = (x - self._mu) / sigma
+ return exp(-0.5 * z * z) / (_SQRT2PI * sigma)
def cdf(self, x):
"Cumulative distribution function. P(X <= x)"
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