what's the precision of fractions.Fraction?

Hrvoje Niksic hniksic at xemacs.org
Sat Nov 20 12:53:25 CET 2010


Mark Dickinson <dickinsm at gmail.com> writes:

> On Nov 19, 3:29 pm, RJB <rbott... at csusb.edu> wrote:
>> Does Fractions remove common factors the way it should?
>>
>> If it does and you want to find the closest fraction with a smaller
>> denominator i think tou'll need some number theory and continued
>> fractions.
>
> Or perhaps just use the existing Fraction.limit_denominator method
> (which does indeed use some number theory and continued fractions):
>
>>>> from fractions import Fraction
>>>> from math import pi
>>>> Fraction.from_float(pi).limit_denominator(1000)
> Fraction(355, 113)

People, this is exactly what http://xkcd.com/353/ is about.



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