[Python-checkins] r83277 - python/branches/py3k/Doc/library/functions.rst

mark.dickinson python-checkins at python.org
Fri Jul 30 15:13:02 CEST 2010


Author: mark.dickinson
Date: Fri Jul 30 15:13:02 2010
New Revision: 83277

Log:
Add note about surprising behaviour from round function.

Modified:
   python/branches/py3k/Doc/library/functions.rst

Modified: python/branches/py3k/Doc/library/functions.rst
==============================================================================
--- python/branches/py3k/Doc/library/functions.rst	(original)
+++ python/branches/py3k/Doc/library/functions.rst	Fri Jul 30 15:13:02 2010
@@ -972,6 +972,13 @@
    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:


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