def kaboom(list, n):
    print list[n]            # trigger IndexError

try:
    kaboom([0, 1, 2], 3)
except IndexError:           # catch exception here
    print 'Hello world!'     


###


MyError = "my error"

def stuff(file):
    raise MyError

file = open('data', r)       # open a file
try:
    stuff(file)              # raises exception
finally:
    file.close()             # always close file