Question

class ShortInputException(Exception):
'''A user-defined exception class.'''
          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 ShortInputException, x:
           print 'ShortInputException: The input was of length %d, \
           was expecting at least %d' % (x.length, x.atleast)

I dont understand the syntax of this line: except ShortInputException, x:

what is x here for ??
and why is it acting as an object ???

waht does this line do ? : Exception.__init__(self)

Thanks

Answer 1

except ShortInputException, x:

catches an exception of class ShortInputException and binds the instance of the exception object to x.

The more common syntax for this is

except ShortInputException as x

which is to be preferred as described in PEP3110. Unless you need to support Python 2.5, you should use the as version.

---

Exception.__init__(self)

calls the constructor for the super class, the class that this user defined class derives from.