March 20, 2010
3:11 p.m.
Mark Dickinson <dickinsm <at> gmail.com> writes:
On Fri, Mar 19, 2010 at 9:50 PM, Guido van Rossum <guido <at> python.org>
wrote:
There is one choice which I'm not sure about. Should a mixed float/Decimal operation return a float or a Decimal?
I'll just say that it's much easier to return a Decimal if you want to be able to make guarantees about rounding behaviour, basically because floats can be converted losslessly to Decimals. I also like the fact that the decimal module offers more control (rounding mode, precision, flags, wider exponent range) than float.
A problem, though, is that decimals are much slower than floats. If you have a decimal creeping in some part of a calculation it could degrade performance quite a bit. Regards Antoine.