Wybiral

from operator import add, sub, mul, div, gt, lt, eq

def gcd(frac):
    mod = frac[0] % frac[1]
    return frac[1] if not(mod) else gcd((frac[1], mod))

class Fraction:

    def __init__(self, *args):
        if len(args) == 2:
            self.frac = args
        else:
            arg = args[0]
            if isinstance(arg, Fraction):
                self.frac = arg.frac
            elif hasattr(arg, "__iter__"):
                self.frac = arg
            elif isinstance(arg, int):
                self.frac = arg, 1
            elif isinstance(arg, float):
                d = 10 ** len(("%f" % arg).split(".")[1])
                self.frac = (int(arg * d), d)
            elif isinstance(arg, str):
                self.frac = map(int, arg.split('/'))

        Frac = Fraction
        self.__getitem__ = self.frac.__getitem__
        self.__iter__, self.__len__ = self.frac.__iter__, self.frac.__len__
        self.__cmp__ = lambda x: cmp(float(self), float(Frac(x)))
        self.__str__ = lambda: "%d/%d" % tuple(self.frac)
        self.__float__ = lambda: div(*map(float, self))
        self.__int__ = lambda: div(*self)
        self.__mul__ = lambda x: Frac(map(mul, self, Frac(x)))
        self.__div__ = lambda x: self * reversed(Frac(x))
        op = lambda func, a, b: (func(*map(mul, a, b)), a[1] * b[0])
        self.__add__ = lambda x: Frac(op(add, self, Frac(x).recip()))
        self.__sub__ = lambda x: Frac(op(sub, self, Frac(x).recip()))
        self.recip = lambda: Frac(reversed(self))
        self.frac = map(div, self, [gcd(self)] * 2)

if __name__ == "__main__":
    ops = {'+':add, '-':sub, '*':mul, '/':div, '>':gt, '<':lt, '=':eq}
    for fracs in (("1/2", 0.25), (1, (1, 3)), (0.01, [1, 5])):
        a, b = map(Fraction, fracs)
        print "For fractions '%s' and '%s'..." % (a, b)
        print "As floats: '%s' and '%s'" % (float(a), float(b))
        for op, func in ops.items():
            print "%s %s %s is %s" % (a, op, b, func(a, b))
    print float(Fraction("1/2"))