自定义异常

异常通常直接或间接的从Exception类派生

#! /usr/bin/python

import sys,os

class MyError(Exception):
    def __init__(self,value):
        self.value = value
    def __str__(self):
        return repr(self.value)

try:
    f = open('myfile.txt')

except IOError, (errno,strerror):
    print "I/O error(%s): %s" %(errno,strerror)

#raise NameError, "Just for test! "
raise MyError, "my error is raised!"

the result:

Traceback (most recent call last):
  File "test.py", line 18, in <module>
    raise MyError, "my error is raised!"
__main__.MyError: 'my error is raised!'