bad = 'bad'  
  
try:  
    raise bad  
except bad:  
    print 'Got Bad!'  

Traceback (most recent call last):  
  File "D:\Learn\Python\Learn.py", line 4, in <module>  
    raise bad  
TypeError: exceptions must be old-style classes or derived from BaseException, not str

class Bad(Exception):  
    pass  
  
def raiseException():  
    raise Bad()  
  
try:  
    raiseException()  
except Bad:  
    print 'Got Bad!'