From e6dc53120d52f58057fd1a6d666d21cb9d71c08d Mon Sep 17 00:00:00 2001 From: Mark Dickinson Date: Wed, 7 Jan 2009 17:48:33 +0000 Subject: Issue #4869: clarify documentation for random.expovariate. --- Doc/library/random.rst | 8 +++++--- Lib/random.py | 8 +++++--- 2 files changed, 10 insertions(+), 6 deletions(-) diff --git a/Doc/library/random.rst b/Doc/library/random.rst index 858888c..63c4bc7 100644 --- a/Doc/library/random.rst +++ b/Doc/library/random.rst @@ -210,9 +210,11 @@ be found in any statistics text. .. function:: expovariate(lambd) - Exponential distribution. *lambd* is 1.0 divided by the desired mean. (The - parameter would be called "lambda", but that is a reserved word in Python.) - Returned values range from 0 to positive infinity. + Exponential distribution. *lambd* is 1.0 divided by the desired + mean. It should be nonzero. (The parameter would be called + "lambda", but that is a reserved word in Python.) Returned values + range from 0 to positive infinity if *lambd* is positive, and from + negative infinity to 0 if *lambd* is negative. .. function:: gammavariate(alpha, beta) diff --git a/Lib/random.py b/Lib/random.py index 5879340..8b4c38e 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -413,9 +413,11 @@ class Random(_random.Random): def expovariate(self, lambd): """Exponential distribution. - lambd is 1.0 divided by the desired mean. (The parameter would be - called "lambda", but that is a reserved word in Python.) Returned - values range from 0 to positive infinity. + lambd is 1.0 divided by the desired mean. It should be + nonzero. (The parameter would be called "lambda", but that is + a reserved word in Python.) Returned values range from 0 to + positive infinity if lambd is positive, and from negative + infinity to 0 if lambd is negative. """ # lambd: rate lambd = 1/mean -- cgit v0.12