good idea. I will add that.
On Nov 14, 9:35 am, Jonathan Lundell <jlund...@pobox.com> wrote:
> On Nov 13, 2009, at 9:43 PM, mdipierro wrote:
>
>
>
>
>
> > Fascinating. As an experiment I replaced str with repr and it usually
> > works with float. Float is better then integer because allows
> > migrations from one decimal type to float and vice versa and allows
> > for expressions involving different field types without major errors.
>
> > The problem is that when it fails, it has major failures.
>
> > Everybody should be aware that there will be much bigger rounding
> > errors with type='decimal' on sqlite than with type='double'. With
> > double the rounding errors will be of the order of required decimal
> > precision, much bigger than double precision.
>
> > That is because is
>
> >>>> a = 0.3/3 # is float
> >>>> print str(a)[0:5]
> > 0.1
>
> > while
>
> >>>> from decimal import Decimal
> >>>> b=Decimal(repr(a)[0:5])
> >>>> print b
> > 0.099
>
> > Conversions like the one above are necessary step to get data in/out
> > of database.
>
> > The more I look into this the more I think we should not support it if
> > the database does not support it.
>
> Perhaps the string conversion should use a formatted string, with the
> precision of the database field.
>
>
>
> > Massimo
>
> > On Nov 13, 9:27 pm, Jonathan Lundell <jlund...@pobox.com> wrote:
> >> On Nov 13, 2009, at 4:36 PM, Massimo Di Pierro wrote:
>
> >>> In theory double has 53 bits. Yet I tried and it does not seem to work
> >>> properly. It rounds to the cents. You may want to try the attached
> >>> files. Perhaps I am doing something wrong.
>
> >> I'm not advocating floating point; I think it's a pain, and if integer is
> >> working, that's better. But....
>
> >>>>> from decimal import *
> >>>>> b = Decimal("1234567891.987654321")
> >>>>> b
>
> >> Decimal('1234567891.987654321')>>> float(b)
> >> 1234567891.9876542
> >>>>> str(float(b))
> >> '1234567891.99'
> >>>>> repr(float(b))
>
> >> '1234567891.9876542'
>
> >> I haven't checked, but it looks like an artifact of float.str.
>
>
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