Python 异常捕获，自定义异常

class MyException(TypeError):     # 自定义异常，继承TypeError
    def __index__(self, arg):
        self.args = arg
def addTwoNumber(a,b):
    try:
        if isinstance(a,str) or isinstance(a,str):
            raise MyException('我需要的是数值类型，而你给我的却是字符串')
        else:
            print(a + b)
    except MyException as err:
        print(err)
    except Exception as err:
        print(err)
    else:
        print('我是else')
    finally:
        print('我是finally')
addTwoNumber(13,12)
addTwoNumber('a',12)