From: Mark Dickinson <dickinsm@gmail.com>
Date: Fri, 30 Jul 2010 13:13:02 +0000 (+0000)
Subject: Add note about surprising behaviour from round function.
X-Git-Tag: v3.2a1~39
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=c4fbcdc4c80eb733f923b1c9a5a5c52399acb958;p=thirdparty%2FPython%2Fcpython.git

Add note about surprising behaviour from round function.
---

diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index 8a413f4bc81a..5c21f34a3f13 100644
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -972,6 +972,13 @@ are always available.  They are listed here in alphabetical order.
    The return value is an integer if called with one argument, otherwise of the
    same type as *x*.
 
+   .. note::
+
+      The behavior of :func:`round` for floats can be surprising: for example,
+      ``round(2.675, 2)`` gives ``2.67`` instead of the expected ``2.68``.
+      This is not a bug: it's a result of the fact that most decimal fractions
+      can't be represented exactly as a float.  See :ref:`tut-fp-issues` for
+      more information.
 
 .. function:: set([iterable])
    :noindex: