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 = 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()< pre>

 #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:  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  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)