On Fri, Aug 23, 2013 at 9:30 PM, Steven D'Aprano
<steve+comp.lang.pyt...@pearwood.info> wrote:
> Is there a fast way to convert a Decimal into a pair of numbers numerator/
> denominator? It *must* be exact, but it doesn't have to be simplest form.
> For example, Decimal("0.5") => (5, 10) would be okay, although (1, 2)
> would be preferred.
>
>
> I've tried this function:
>
> def convert(d):
> sign, digits, exp = d.as_tuple()
> num = int(''.join([str(digit) for digit in digits]))
> if sign: num = -num
> return num, 10**-exp
>
>
> which is faster, but not fast enough. Any suggestions?
I time this function at about 33% faster than your version for a
six-digit decimal, and almost 50% faster for a 12-digit decimal. My
guess would be because it's not calling str() on every individual
digit.
def convert(d):
exp = d.as_tuple().exponent
num = int(d.scaleb(-exp))
return num, 10**-exp
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