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Groups > comp.lang.python > #107041
| From | Tony van der Hoff <tony@vanderhoff.org> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Re: sum accuracy |
| Date | 2016-04-15 11:39 +0100 |
| Message-ID | <mailman.13.1460717963.6324.python-list@python.org> (permalink) |
| References | (2 earlier) <5710B365.5040903@chamonix.reportlab.co.uk> <CAHVvXxSub2Z2j6eedm3zQr7v2aYWMhmGYzXTtx+SPrcAFgXFtw@mail.gmail.com> <mailman.11.1460712984.6324.python-list@python.org> <87d1prw5b7.fsf@bsb.me.uk> <5710C4F1.8050805@vanderhoff.org> |
On 15/04/16 11:10, Ben Bacarisse wrote: > Oscar Benjamin <oscar.j.benjamin@gmail.com> writes: > >> On 15 April 2016 at 10:24, Robin Becker <robin@reportlab.com> wrote: > <snip> >>> yes indeed summation is hard :( >> >> Not with Fraction it isn't: >> >> from fractions import Fraction >> >> def exact_sum(nums): >> return sum(map(Fraction, nums)) >> >> This will give you the exact result with precisely zero rounding >> error. You can convert it to float at the end. > > Just a word of warning for people new to numerical work: there's no > rounding error, but unless you start with Fraction objects you still > have input or conversion errors. The uninitiated might expect > > exact_sum([0.3, 0.7]) > > to be 1. > So I'm uninitiated: NameError: name 'exact_sum' is not defined I appreciate the word of warning, but, in my case, it's not helpful. -- Tony van der Hoff | mailto:tony@vanderhoff.org Buckinghamshire, England |
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Re: sum accuracy Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2016-04-15 10:36 +0100
Re: sum accuracy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-04-15 11:10 +0100
Re: sum accuracy Tony van der Hoff <tony@vanderhoff.org> - 2016-04-15 11:39 +0100
Re: sum accuracy Jussi Piitulainen <jussi.piitulainen@helsinki.fi> - 2016-04-15 14:31 +0300
Re: sum accuracy Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-04-15 08:11 -0400
Re: sum accuracy Oscar Benjamin <oscar.j.benjamin@gmail.com> - 2016-04-15 14:49 +0100
Re: sum accuracy Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-04-15 17:54 +0100
Re: sum accuracy Matt Wheeler <m@funkyhat.org> - 2016-04-15 18:04 +0100
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