Python用户自定义异常的实现

#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.用户自定义异常类型
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")
 
#2.手动抛出用户自定义类型异常
def name_Test():
    name = input("enter your naem:")
    if len(name)>4:
      raise TooLongExceptin(len(name)) #抛出异常很简单，使用raise即可,但是没有处理，即捕捉
    else :
      print(name)
 
#调用函数，执行
name_Test()
-----------------执行时满足条件后抛出一个用户定义的异常如下：--------------------------------------
enter your naem:是打发斯蒂芬
Traceback (most recent call last):
姓名长度是6，超过长度了
 File "D:/pythoyworkspace/file_demo/Class_Demo/extion_demo.py", line 21, in <module>
  name_Test()
__main__.TooLongExceptin: <exception str() failed>

#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)