Exception Handling

>>> while True: ...     try: ...         x = int(raw_input("Please enter a number: ")) ...         break ...     except ValueError: ...         print "Oops!  That was no valid number.  Try again..." ...

raise error

>>> try: ...     raise NameError('HiThere') ... except NameError: ...     print 'An exception flew by!' ...     raise ... An exception flew by! Traceback (most recent call last):   File "
     
      ", line 2, in ? NameError: HiThere
     

user-defined exceptions

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

>>> raise MyError("oops!") Traceback (most recent call last):   File "
     
      ", line 1, in 
      
        __main__.MyError: 'oops!'
      
     

define clean-up action

>>> try: ...     raise KeyboardInterrupt ... finally: ...     print 'Goodbye, world!' ... Goodbye, world! KeyboardInterrupt