How about adding rational fraction to Python?

[Paul Rubin]

Mark Dickinson <dickinsm at gmail.com> writes:
> def mean(number_list):
>     return sum(number_list)/len(number_list)
> 
> If you pass a list of floats, complex numbers, Fractions, or Decimal
> instances to mean() then it'll work just fine.  But if you pass
>  a list of ints or longs, it'll silently return the wrong result.

So use:  return sum(number_list) / float(len(number_list))
That makes it somewhat more explicit what you want.  Otherwise
I wouldn't be so sure the integer result is "wrong".