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| author | Mark Dickinson <dickinsm@gmail.com> | 2009-01-07 17:48:33 +0000 |
|---|---|---|
| committer | Mark Dickinson <dickinsm@gmail.com> | 2009-01-07 17:48:33 +0000 |
| commit | e6dc53120d52f58057fd1a6d666d21cb9d71c08d (patch) | |
| tree | a91c10c8f2856264f7f213e0f98278b431ec58bc | |
| parent | fde5b803d8f2437e5311bae73c970c7205fcd925 (diff) | |
| download | cpython-git-e6dc53120d52f58057fd1a6d666d21cb9d71c08d.tar.gz | |
Issue #4869: clarify documentation for random.expovariate.
| -rw-r--r-- | Doc/library/random.rst | 8 | ||||
| -rw-r--r-- | Lib/random.py | 8 |
2 files changed, 10 insertions, 6 deletions
diff --git a/Doc/library/random.rst b/Doc/library/random.rst index 858888c9c5..63c4bc71a5 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 5879340a8d..8b4c38edb1 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 |