Zachary Ware added the comment: Hi Rihards,
This is not a bug, this is an example of the limitations of binary floating point arithmetic. See http://docs.python.org/3/tutorial/floatingpoint.html for more information. For explanation by demonstration, have a look at this: Python 3.3.2 (v3.3.2:d047928ae3f6, May 16 2013, 00:03:43) [MSC v.1600 32 bit (Intel)] on win32 Type "help", "copyright", "credits" or "license" for more information. >>> from decimal import Decimal as D >>> D(11.29) Decimal('11.28999999999999914734871708787977695465087890625') >>> D(6.29) Decimal('6.29000000000000003552713678800500929355621337890625') >>> D(11.30) Decimal('11.300000000000000710542735760100185871124267578125') >>> D(6.30) Decimal('6.29999999999999982236431605997495353221893310546875') >>> D(11.291) Decimal('11.291000000000000369482222595252096652984619140625') >>> D(6.291) Decimal('6.291000000000000369482222595252096652984619140625') >>> 11.29 - 6.29 4.999999999999999 >>> 11.30 - 6.30 5.000000000000001 >>> 11.291 - 6.291 5.0 >>> D(11.29) - D(6.29) Decimal('4.999999999999999111821580300') >>> D(11.30) - D(6.30) Decimal('5.000000000000000888178419700') >>> D(11.291) - D(6.291) Decimal('5.000000000000000000000000000') >>> For future reference, "bug?" isn't very useful as an issue title :). The title should be as brief a summary of the possible bug as you can come up with, or at least mention which part(s) of Python are affected. ---------- nosy: +zach.ware resolution: -> invalid stage: -> committed/rejected status: open -> closed title: bug? -> bug in float arithmetic? type: -> behavior versions: +Python 3.3 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue20533> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
