Mark Dickinson <dicki...@gmail.com> added the comment: Thanks for the report.
This is fixed in Python 3.1 (except on a few unusual hardware/OS combinations): Python 3.1rc1+ (py3k:73252, Jun 6 2009, 10:35:36) [GCC 4.0.1 (Apple Computer, Inc. build 5367)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> round(697.04157958254996, 10) 697.0415795825 It's a "won't fix" for Python 2.x. Rounding to 10 decimal places involves multiplying by 10**10., rounding to the nearest integer, then dividing by 10**10. again; the problem in this case is that multiplication by 10.**10 is inexact, and the error involved in the multiplication by 10**10. pushes the value from the 'round down' region into the 'round up region': Python 2.7a0 (trunk:73252, Jun 6 2009, 10:16:08) [GCC 4.0.1 (Apple Computer, Inc. build 5367)] on darwin Type "help", "copyright", "credits" or "license" for more information. >>> 697.04157958254996 * 10**10 6970415795825.5 [38623 refs] There's no easy way to fix this, short of using multiple-precision arithmetic to do the rounding (which is what Python 3.1 does). By the way, Python's float can't represent the number 697.04157958254996 exactly (assuming IEEE 754 arithmetic): the closest it gets is the value: 697.041579582549957194714806973934173583984375 but the repr of a float (in Python 3.0 and 2.x) only produces 17 significant digits, since that's enough to guarantee that the repr() value evaluates back to the correct float (assuming correct rounding). ---------- nosy: +marketdickinson resolution: -> wont fix status: open -> closed _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue6228> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
