what's the precision of fractions.Fraction?

Daniel Fetchinson fetchinson at googlemail.com
Thu Nov 18 19:17:51 CET 2010

>> I do a recursive evaluation of an expression involving fractions and
>> unsurprisingly the numerator and denominator grows pretty quickly.
>> After 10-20 iterations the number of digits in the numerator and
>> denominator (as integers) reaches 80-100. And I'm wondering until what
>> point I can trust the result since I'm using fractions.Fraction for
>> the whole procedure. Are Fraction's infinite precision? Or will I get
>> some sort of an exception if python is not able to represent the
>> numerator and/or denominator as integers?
> Since fractions are represented as a pair of integers, and since python
> integers have unlimited precision, I would guess that fractions also have
> unlimited precision.  You could check the code if you want to be absolutely
> sure.

Sounds reasonable, thanks a lot,

Psss, psss, put it down! - http://www.cafepress.com/putitdown

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