except ShortInputException,x中逗号

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

 try:
     s = raw_input('Enter something --> ')

     if len(s) < 3 :
         raise ShortInputException(len(s), 3)
 except EOFError:
     print '\nWhy did you do an EOF on me?'
 except ShortInputException, x:
     print 'ShortInputException: The input was of length %d, \
           was expecting at least %d' % (x.length, x.atleast)
 else:
     print 'No exception was raised.' 

x就是 ShortInputException的对象
这是python 2.6之前的语法
2.6之后建议使用 except ShortInputException as x: