From: Raymond Hettinger <rhettinger@users.noreply.github.com>
Date: Wed, 1 Dec 2021 01:25:57 +0000 (-0600)
Subject: bpo-45876:  Have stdev() also use decimal specific square root. (GH-29869)
X-Git-Tag: v3.11.0a3~79
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=0aa0bd056349f73de9577ccc38560c1d01864d51;p=thirdparty%2FPython%2Fcpython.git

bpo-45876:  Have stdev() also use decimal specific square root. (GH-29869)
---

diff --git a/Lib/statistics.py b/Lib/statistics.py
index 9f1efa21b15e..ff19ce9672d3 100644
--- a/Lib/statistics.py
+++ b/Lib/statistics.py
@@ -920,9 +920,8 @@ def stdev(data, xbar=None):
         raise StatisticsError('stdev requires at least two data points')
     T, ss = _ss(data, xbar)
     mss = ss / (n - 1)
-    if hasattr(T, 'sqrt'):
-        var = _convert(mss, T)
-        return var.sqrt()
+    if issubclass(T, Decimal):
+        return _decimal_sqrt_of_frac(mss.numerator, mss.denominator)
     return _float_sqrt_of_frac(mss.numerator, mss.denominator)