Adopt Nick's suggestion for useful default arguments.
Clean-up floating point issues by adding true division and float constants.
diff --git a/Doc/library/random.rst b/Doc/library/random.rst
index 505cc81..a064ac4 100644
--- a/Doc/library/random.rst
+++ b/Doc/library/random.rst
@@ -193,7 +193,12 @@
.. function:: triangular(low, high, mode)
Return a random floating point number *N* such that ``low <= N < high``
- and with the specified *mode* between those bounds.
+ and with the specified *mode* between those bounds.
+
+ If *mode* is not specified or is ``None``, it defaults to the midpoint
+ between the upper and lower bounds, producing a symmetric distribution.
+
+ The default values for *low* and *high* are zero and one.
.. function:: betavariate(alpha, beta)
diff --git a/Lib/random.py b/Lib/random.py
index 13125e2..bd8679f 100644
--- a/Lib/random.py
+++ b/Lib/random.py
@@ -39,6 +39,7 @@
"""
+from __future__ import division
from warnings import warn as _warn
from types import MethodType as _MethodType, BuiltinMethodType as _BuiltinMethodType
from math import log as _log, exp as _exp, pi as _pi, e as _e, ceil as _ceil
@@ -353,7 +354,7 @@
## -------------------- triangular --------------------
- def triangular(self, low, high, mode):
+ def triangular(self, low=0.0, high=1.0, mode=None):
"""Triangular distribution.
Continuous distribution bounded by given lower and upper limits,
@@ -363,10 +364,10 @@
"""
u = self.random()
- c = (mode - low) / (high - low)
+ c = 0.5 if mode is None else (mode - low) / (high - low)
if u > c:
- u = 1 - u
- c = 1 - c
+ u = 1.0 - u
+ c = 1.0 - c
low, high = high, low
return low + (high - low) * (u * c) ** 0.5