Groups > comp.lang.python > #20690

Re: Python math is off by .000000000000045

Path	csiph.com!x330-a1.tempe.blueboxinc.net!usenet.pasdenom.info!goblin1!goblin2!goblin.stu.neva.ru!news.stack.nl!newsfeed.xs4all.nl!newsfeed6.news.xs4all.nl!xs4all!newsgate.cistron.nl!newsgate.news.xs4all.nl!post.news.xs4all.nl!not-for-mail
Return-Path	<python-python-list@m.gmane.org>
X-Original-To	python-list@python.org
Delivered-To	python-list@mail.python.org
X-Spam-Status	OK 0.052
X-Spam-Evidence	'H': 0.91; 'S': 0.02; 'subject:Python': 0.05; 'python': 0.08; '>>>>': 0.09; 'bug?': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'url:95': 0.09; '18:13,': 0.16; 'wrote:': 0.18; 'header:In-Reply-To:1': 0.22; 'math': 0.24; 'skip:1 30': 0.29; 'subject: .': 0.29; 'thanks': 0.32; 'there': 0.33; 'header :User-Agent:1': 0.33; 'header:X-Complaints-To:1': 0.34; 'from:addr:yahoo.co.uk': 0.34; 'numbers.': 0.34; 'to:addr:python- list': 0.35; 'google': 0.35; 'received:org': 0.36; 'mathematical': 0.38; 'point': 0.40; 'to:addr:python.org': 0.40; 'url:%0': 0.60; 'simple': 0.61; 'taylor': 0.67; 'url:%2b': 0.67; 'url:i': 0.74; 'received:as13285.net': 0.84; 'url:530': 0.84; 'url:74': 0.84; 'aka': 0.91; 'received:2': 0.91; 'only:': 0.93
X-Injected-Via-Gmane	http://gmane.org/
To	python-list@python.org
From	Mark Lawrence <breamoreboy@yahoo.co.uk>
Subject	Re: Python math is off by .000000000000045
Date	Wed, 22 Feb 2012 18:24:37 +0000
References	<CAO+9iGcg5aTuv1y_GYEMJAPw8zhOmS=tDKTjVsaBe77Q5cd6TA@mail.gmail.com>
Mime-Version	1.0
Content-Type	text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding	7bit
X-Gmane-NNTP-Posting-Host	host-2-97-68-111.as13285.net
User-Agent	Mozilla/5.0 (Windows NT 6.0; rv:10.0.2) Gecko/20120216 Thunderbird/10.0.2
In-Reply-To	<CAO+9iGcg5aTuv1y_GYEMJAPw8zhOmS=tDKTjVsaBe77Q5cd6TA@mail.gmail.com>
X-Antivirus	avast! (VPS 120222-0, 22/02/2012), Outbound message
X-Antivirus-Status	Clean
X-BeenThere	python-list@python.org
X-Mailman-Version	2.1.12
Precedence	list
List-Id	General discussion list for the Python programming language <python-list.python.org>
List-Unsubscribe	<http://mail.python.org/mailman/options/python-list>, <mailto:python-list-request@python.org?subject=unsubscribe>
List-Archive	<http://mail.python.org/pipermail/python-list>
List-Post	<mailto:python-list@python.org>
List-Help	<mailto:python-list-request@python.org?subject=help>
List-Subscribe	<http://mail.python.org/mailman/listinfo/python-list>, <mailto:python-list-request@python.org?subject=subscribe>
Newsgroups	comp.lang.python
Message-ID	<mailman.50.1329935101.3037.python-list@python.org> (permalink)
Lines	25
NNTP-Posting-Host	2001:888:2000:d::a6
X-Trace	1329935101 news.xs4all.nl 6905 [2001:888:2000:d::a6]:41065
X-Complaints-To	abuse@xs4all.nl
Xref	x330-a1.tempe.blueboxinc.net comp.lang.python:20690

Show key headers only | View raw

On 22/02/2012 18:13, Alec Taylor wrote:
> Simple mathematical problem, + and - only:
>
>>>> 1800.00-1041.00-555.74+530.74-794.95
> -60.950000000000045
>
> That's wrong.
>
> Proof
> http://www.wolframalpha.com/input/?i=1800.00-1041.00-555.74%2B530.74-794.95
> -60.95 aka (-(1219/20))
>
> Is there a reason Python math is only approximated? - Or is this a bug?
>
> Thanks for all info,
>
> Alec Taylor

Please google for floating point numbers.

-- 
Cheers.

Mark Lawrence.

Back to comp.lang.python | Previous | Next | Find similar | Unroll thread

Thread

Re: Python math is off by .000000000000045 Mark Lawrence <breamoreboy@yahoo.co.uk> - 2012-02-22 18:24 +0000

csiph-web