def test1():

    print("---test1--")

    print(num)

    print('---test1 over---')

def test2():

    print('---test2---')

    test1()

    print('----test2 over ----')

def test3():

    try:

        print('----test3---')

        test2()

        print('----test3 ovrer')

    except Exception as result:

        print("捕获到了异常，异常时%s"%result)

test3()

----test3---

---test2---

---test1--

捕获到了异常，异常时name 'num' is not defined

class ShortInputException(Exception):

    '''自定义的异常类'''

    def __init__(self, length, atleast):

        #super().__init__()

        self.length = length

        self.atleast = atleast

def main():

    try:

        s = input('请输入 --> ')

        if len(s) < 3:

            # raise引发一个你定义的异常

            raise ShortInputException(len(s), 3)

    except ShortInputException as result:#x这个变量被绑定到了错误的实例

        print('ShortInputException: 输入的长度是 %d,长度至少应是 %d'% (result.length, result.atleast))

    else:

        print('没有异常发生.')

main()

class Test(object):

    def __init__(self, switch):

        self.switch = switch #开关

    def calc(self, a, b):

        try:

            return a/b

        except Exception as result:

            if self.switch:

                print("捕获开启，已经捕获到了异常，信息如下:")

                print(result)

            else:

                #重新抛出这个异常，此时就不会被这个异常处理给捕获到，从而触发默认的异常处理

                raise

a = Test(True)

a.calc(11,0)

print("----------------------华丽的分割线----------------")

a.switch = False

a.calc(11,0)