class operate(object):
    def __init__(self, a, b):
        self.a = a
        self.b = b
    def add(self):
        return self.a + self.b
    def multi(self):
        return self.a * self.b

def main(a, b, method):
    Oper = operate(a, b)
    method_dict = {
   "add":Oper.add(), "multi":Oper.multi()}
    res = method_dict[method]
    return res

if __name__ == "__main__":
    res1 = main(2, 3, "multi")
    res2 = main(2, 3, "add")
    print(res1, res2)

输出：

6	5

其实就是 字典 代替很多的 if...else...