python运算符重载案例

'''
*   自定义一个Ration类（有理数类）
*   把有理数的正负判断功能移动到分子，把分数看作数组other [0]=分子，[1]=分母
*   运算符重载还有 __mod__(self)求余.__contians__(self，value)检查其成员资格,在本例中没体现
'''
def gcd(a,b):#考虑到正负数，需要每次递归都要把a,b取绝对值
    a=abs(a)
    b=abs(b)
    if a<b:
        a,b=b,a
    if b ==0:
        return a
    else:
        return gcd(b,a%b)
class Ration:
    def __init__(self,numberator=0,denominator=1):#分子，分母
        divisor=gcd(numberator,denominator)
        self.__numberator=(1 if denominator >0 else -1)*int(numberator/divisor)
        self.__denominator=int(abs(denominator)/divisor)

# + - * /：
    def __add__(self,secondRation):
       n= self.__numberator * secondRation[1]+ self.__denominator * secondRation[0]
       m= self.__denominator*secondRation[1]
       return Ration(n,m)

    def __sub__(self,secondRation):
        n=self.__numberator*secondRation[1]-self.__denominator*secondRation[0]
        m=self.__denominator*secondRation[1]
        return Ration(n,m)

    def __mul__(self,secondRation):
        n=self.__numberator*secondRation[0]
        m=self.__denominator*secondRation[1]
        return Ration(n,m)

    def __truediv__(self,secondRation):
        n=self.__numberator*secondRation[1]
        m=self.__denominator*secondRation[0]
        return Ration(n,m)

# 返回格式
    def __float__(self):
        return self.__numberator/self.__denominator

    def __int__(self):
        return int(self.__float__())

    def __str__(self):
        if self.__denominator==1:
            return str(self.__numberator)
        else :
            return str(self.__numberator)+"/"+str(self.__denominator)

    def __getitem__(self,index):
        #下标运算符
        if index==0:
            return self.__numberator
        else:
            return self.__denominator

#比较
    def __cmp__(self,secondRation):
        temp=self.__sub__(secondRation)
        if temp[0]>0:
            return 1
        elif temp[0]==0:
            return 0
        else:
            return -1
    def __lt__(self,secondRation):
        return  self.__cmp__(secondRation)<0

    def __le__(self,secondRation):
        return self.__cmp__(secondRation)<=0

    def __eq__(self,secondRation):
        return  self.__cmp__(secondRation)==0

    def __ne__(self,secondRation):
        return  self.__cmp__(secondRation)!=0

    def __gt__(self,secondRation):
        return self.__cmp__(secondRation)>0

    def __ge__(self,secondRation):
        return  self.__cmp__(secondRation)>=0

def main():
    r1=Ration(4,2)
    r2=Ration(2,3)
    print(r1,"+",r2,"=",r1+r2)
    print(r1,"-",r2,"=",r1-r2)
    print(r1,"*",r2,"=",r1*r2)
    print(r1,"/",r2,"=",r1/r2)
    print(r1>r2)
    print(r1==r2)
    print(r1<r2)
main()