diff options
| -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 da0e6632f3..82d2555cee 100644 --- a/Doc/library/random.rst +++ b/Doc/library/random.rst @@ -169,9 +169,11 @@ 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 70603ca2ae..95f44113bf 100644 --- a/Lib/random.py +++ b/Lib/random.py @@ -396,9 +396,11 @@ 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 |