自学教程：python用户自定义异常的实例讲解

class ShortInputException(Exception):    def __init__(self, length, atleast):        self.length = length        self.atleast = atleastdef 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()

#1.用户自定义异常类型，只要该类继承了Exception类即可，至于类的主题内容用户自定义，可参考官方异常类class TooLongExceptin(Exception):  "this is user's Exception for check the length of name "  def __init__(self,leng):    self.leng = leng  def __str__(self):    print("姓名长度是"+str(self.leng)+"，超过长度了")

 #1.捕捉用户手动抛出的异常，跟捕捉系统异常方式一样def name_Test():  try:    name = input("enter your naem:")    if len(name)>4:      raise TooLongExceptin(len(name))    else :      print(name)   except TooLongExceptin,e_result: #这里异常类型是用户自定义的    print("捕捉到异常了")    print("打印异常信息：",e_result) #调用函数，执行name_Test()==========执行结果如下：==================================================enter your naem:aaafsdf捕捉到异常了Traceback (most recent call last):打印异常信息： 姓名长度是7，超过长度了姓名长度是7，超过长度了 File "D:/pythoyworkspace/file_demo/Class_Demo/extion_demo.py", line 16, in name_Test  raise TooLongExceptin(len(name))__main__.TooLongExceptin: <exception str() failed> During handling of the above exception, another exception occurred: Traceback (most recent call last): File "D:/pythoyworkspace/file_demo/Class_Demo/extion_demo.py", line 26, in <module>  name_Test() File "D:/pythoyworkspace/file_demo/Class_Demo/extion_demo.py", line 22, in name_Test  print("打印异常信息：",e_result)TypeError: __str__ returned non-string (type NoneType)