RE Fractions, for _many people_, decimal.Decimal will work very well.
For layout concerns, fractions are probably a more natural fit (things like 1/3), but Decimal is a great floating point default for a lot of problems. They aren't exact, but a lot of the "normal" floating point weirdness goes away and your results look a lot more human. Highly recommend if you don't have a perf reason not to.