Stefan Krah added the comment: What needs to be mentioned though is that the context has to be set for unrounded calculations: c = getcontext() c.prec = MAX_PREC c.Emax = MAX_EMAX c.Emin = MIN_EMIN Otherwise some people believe that the bignums are just rounded floating point arithmetic that is expected to be fast (I've seen this misconception somewhere, perhaps on Stackoverflow). ---------- _______________________________________ Python tracker <report@bugs.python.org> <http://bugs.python.org/issue26256> _______________________________________