实现加减乘除计算器

alass myCalc:
def init(self,a,b):
self.a=a
self.b=b
def addition(self,Retain):
return round(self.a + self.b,Retain)

    def subtraction(self, Retain):
        return round(self.a - self.b, Retain)

    def multiplication(self, Retain):
        return round(self.a * self.b, Retain)

    def division(self, Retain):
        return round(self.a / self.b, Retain)

while 1:
get_num1 =input(“请输入第一个数字：”)
opera=input(“请输入运算符：”)
get_num2 =input(“请输入第二位小数：”)
get_retain = input(“请输入保留的小数位数：”)
num1= float(get_num1)
num2=float(get_num2)
retain=int(get_retain)
result=0.00
if opera =="+":
result =myCalc(num1,num2).addition(retain)
elif opera =="-":
result =myCalc(num1,num2).subtraction(retain)
elif opera =="*":
result =myCalc(num1,num2).multiplication(retain)
else:
result = myCalc(num1, num2).division(retain)
print(“结果是：”,result)