exception

ex:

ckass Bad(Exception):

          pass

def test():

      raise  Bad(), "test bad"

try:

    test()

except  Bad, info:

     print "bad", info

else:

    print "else"

finally:

     print "finally"

assert:

raise AssertionError when test evaluates to false

ex:

assert  x<=3, 'x must be larger than 3'

raise:

ex1: raise object

class A:

     pass

def  test():

     raise A()

ex2:  raise string

message="Error"

def test():

      raise  message