bpo-41421: Algebraic simplification for random.paretovariate() (GH-21695)

rhettinger · web-flow · commit 5c3270939c09 · 2020-08-01T01:18:26.000-07:00
diff --git a/Lib/random.py b/Lib/random.py
@@ -749,7 +749,7 @@ def paretovariate(self, alpha):
         # Jain, pg. 495
 
         u = 1.0 - self.random()
-        return 1.0 / u ** (1.0 / alpha)
+        return u ** (-1.0 / alpha)
 
     def weibullvariate(self, alpha, beta):
         """Weibull distribution.
diff --git a/Misc/NEWS.d/next/Library/2020-08-01-00-51-15.bpo-41421.dHKRVB.rst b/Misc/NEWS.d/next/Library/2020-08-01-00-51-15.bpo-41421.dHKRVB.rst
@@ -0,0 +1,3 @@
+Make an algebraic simplification to random.paretovariate().  It now is
+slightly less subject to round-off error and is slightly faster. Inputs that
+used to cause ZeroDivisionError now cause an OverflowError instead.

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,3 @@`
	`1`	`+Make an algebraic simplification to random.paretovariate(). It now is`
	`2`	`+slightly less subject to round-off error and is slightly faster. Inputs that`
	`3`	`+used to cause ZeroDivisionError now cause an OverflowError instead.`