farsi...@gmail.com wrote:
> Thanks all, that's very helpful, sorry to waste your time with a
> common question. I have tried the decimal module and will definitely
> keep using it if I need to do this kind of calculation again.
Try to remember though that the decimal module simply replaces one source
of inaccuracies with another one:
>>> Decimal("1")/Decimal("3")
Decimal('0.3333333333333333333333333333')
>>> _ * 3
Decimal('0.9999999999999999999999999999')
>>> 1./3.
0.33333333333333331
>>> _ * 3
1.0
Sometimes you want floating point, sometimes you want Decimal. You need to
understand the advantages and drawbacks of each in order to make an
informed choice.
>
> I have 1 more question that the floating point article that was linked
> didn't really answer:
>
> >>> x = 0.8
> >>> x
> 0.800000000000004
> >>> x * 5
> 4.0
>
> Shouldn't I be expecting something like 4.0000000000002 ?
>
You should certainly expect that the final result may be a little bit away
from the 'exact' result but rounding errors can work in your favour just as
well as they work against.
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