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Groups > comp.lang.python > #106978
| From | Peter Otten <__peter__@web.de> |
|---|---|
| Newsgroups | comp.lang.python |
| Subject | Accuracy of math.sqrt(), was Re: Serious error in int() function? |
| Date | 2016-04-14 09:46 +0200 |
| Organization | None |
| Message-ID | <mailman.95.1460620029.15650.python-list@python.org> (permalink) |
| References | <52f7516c-8601-4252-ab16-bc30c59c8306@googlegroups.com> <570f3e30$0$665$426a74cc@news.free.fr> <nenhtf$1o6$1@ger.gmane.org> |
ast wrote: > > <martin.spichty@gmail.com> a écrit dans le message de > news:52f7516c-8601-4252-ab16-bc30c59c8306@googlegroups.com... >> Hi, >> >> there may be a serious error in python's int() function: >> >> print int(float(2.8/0.1)) >> >> yields >> >> 27 >> >> instead of 28!! >> >> I am using Python Python 2.7.6, GCC 4.8.2 on Linux Ubuntu. >> >> Is that known? >> Best, >> Martin > > > I have a similar question, so I post my message here. > Hope this will not annoy the OP Well, you "annoy" me ;) Would you please always take the time to come up with a subject line that matches your question. You should also start a new thread. > Is it sure that the square root of a square number is always > an integer ? > > I would not like to get a result as 345.99999999 > > from math import sqrt > >>>>sqrt(16) > 4.0 >>>> sqrt(16).is_integer() > True > >>>> for n in range(1000000): > ... if not sqrt(n**2).is_integer(): > ... print(sqrt(n**2)) > > it seems to work ... but does it work for all integers ? Even if you get an integer it may not be the one you are expecting: >>> sqrt((10**22)**2) == 10**22 True >>> sqrt((10**23)**2) == 10**23 False >>> sqrt((10**23)**2).is_integer() True >>> int(sqrt((10**23)**2)) 99999999999999991611392
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Serious error in int() function? martin.spichty@gmail.com - 2016-04-13 00:41 -0700
Re: Serious error in int() function? Marko Rauhamaa <marko@pacujo.net> - 2016-04-13 10:55 +0300
Re: Serious error in int() function? Alain Ketterlin <alain@universite-de-strasbourg.fr.invalid> - 2016-04-13 10:00 +0200
Re: Serious error in int() function? Peter Otten <__peter__@web.de> - 2016-04-13 10:03 +0200
Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-13 09:04 +0100
Re: Serious error in int() function? Gregory Ewing <greg.ewing@canterbury.ac.nz> - 2016-04-13 23:51 +1200
Re: Serious error in int() function? "ast" <nomail@com.invalid> - 2016-04-14 08:52 +0200
Re: Serious error in int() function? Christian Gollwitzer <auriocus@gmx.de> - 2016-04-14 09:25 +0200
Accuracy of math.sqrt(), was Re: Serious error in int() function? Peter Otten <__peter__@web.de> - 2016-04-14 09:46 +0200
Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-14 08:59 +0100
Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-14 09:13 +0100
Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-14 13:07 +0100
Re: Serious error in int() function? Dennis Lee Bieber <wlfraed@ix.netcom.com> - 2016-04-14 20:36 -0400
Re: Serious error in int() function? Christian Gollwitzer <auriocus@gmx.de> - 2016-04-15 04:38 +0200
Re: Serious error in int() function? John Pote <johnhpote@o2.co.uk> - 2016-04-15 12:05 +0100
Re: Serious error in int() function? alister <alister.ware@ntlworld.com> - 2016-04-15 11:50 +0000
Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-15 09:41 +0100
Re: Serious error in int() function? blindanagram@nowhere.net - 2016-04-15 09:41 +0100
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