我的程序和答案一样，为什么结果 不对？求大神指导
def gcd(a,b):
if b==0:
return a
return gcd(b,a%b)
class Rational(object):
def __init__(self, p, q):
self.p = p
self.q = q
def __add__(self, r):
return Rational(self.p * r.q + self.q * r.p, self.q * r.q)
def __sub__(self, r):
return Rational(self.p * r.q - self.q * r.p, self.q * r.q)
def __mul__(self, r):
return Rational(self.p * r.p , self.q * r.q)
def __div__(self, r):
return Rational(self.p * r.q , self.q * r.p)
def __str__(self):
g=gcd(self.p,self.q)
return'%s%s'%(self.p/g,self.q/g)
__repr__ = __str__
r1 = Rational(1, 2)
r2 = Rational(1, 4)
print r1 + r2
print r1 - r2
print r1 * r2
print r1 / r2
