Jacob- one slight flaw/quirk in Python is if you want floating point
computations you have to specify a floating point.
>>> import decimal
>>> decimal.getcontext().prec = 2
>>> a = decimal.Decimal(2)
>>> b = decimal.Decimal(3)
>>> 100*a/b
Decimal("67")
>>> print 100*a/b
try -
a=decimal.Decimal(2.0)
b = decimal.Decimal(3)
print 100*a/b
Same as writing 100/3.0 as opposed to 100/3. Try it.
On Wed, 19 Jan 2005 22:07:35 -0500, Tim Peters <[EMAIL PROTECTED]> wrote:
> [Jacob S.]
> > I'm having a problem that is ticking me off. (to put it lightly)
> > Why does decimal do this -- I thought that getcontext().prec
> > was number of decimal places?
>
> It's unclear what you mean by "decimal places". From context, you
> _appear_ to mean "number of decimal digits after the radix point". In
> that case, no, that's not what precision means. decimal is a
> floating-point type, not a fixed-point type, and precision is the
> total number of significant digits; the location of the radix point is
> irrelevant. The rules are spelled out in great detail here:
>
> http://www2.hursley.ibm.com/decimal/
>
> > >>> import decimal
> > >>> decimal.getcontext().prec = 2
> > >>> a = decimal.Decimal(2)
> > >>> b = decimal.Decimal(3)
> > >>> 100*a/b
> > Decimal("67")
> > >>> print 100*a/b
> > 67
> > >>>
> >
> > Why does it do this?
>
> It's doing what you told it to do. It would have helped if you had
> been specific about what you wanted it to do. For example, did you
> want 66.67, or what?
>
> > It's really, really, messing things up for me because results are
> > not interpreted in my programs correctly.
>
> Change your code <wink>. Perhaps this is what you wanted?
>
> >>> import decimal
> >>> pennies = decimal.Decimal("0.01")
> >>> a = decimal.Decimal(2)
> >>> b = decimal.Decimal(3)
> >>> print 100*a/b
> 66.66666666666666666666666667
> >>> print (100*a/b).quantize(pennies)
> 66.67
> >>>
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--
'There is only one basic human right, and that is to do as you damn well please.
And with it comes the only basic human duty, to take the consequences.
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