Merged revisions 83277 via svnmerge from

svn+ssh://pythondev@svn.python.org/python/branches/py3k

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  r83277 | mark.dickinson | 2010-07-30 14:13:02 +0100 (Fri, 30 Jul 2010) | 1 line

  Add note about surprising behaviour from round function.
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diff --git a/Doc/library/functions.rst b/Doc/library/functions.rst
index e54faaee4190d95d88d650f33ba416e02e312dc6..f5ff69ede95dac9c690e329d354346d57abf830c 100644 (file)
--- a/Doc/library/functions.rst
+++ b/Doc/library/functions.rst
@@ -1095,6 +1095,14 @@ available.  They are listed here in alphabetical order.
    example, ``round(0.5)`` is ``1.0`` and ``round(-0.5)`` is ``-1.0``).
 
 
+   .. 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: