How to skip sys.exitfunc when unhandled exceptions occur

import atexit

def helloworld():
    print "Hello World!"

atexit.register(helloworld)

raise Exception("Good bye cruel world!")

import sys
import atexit

def clear_atexit_excepthook(exctype, value, traceback):
    atexit._exithandlers[:] = []
    sys.__excepthook__(exctype, value, traceback)

def helloworld():
    print "Hello world!"

sys.excepthook = clear_atexit_excepthook
atexit.register(helloworld)

raise Exception("Good bye cruel world!")

import os
os._exit(0)

import atexit
import os

def helloworld():
    print "Hello World!"

atexit.register(helloworld)

try:
    raise Exception("Good bye cruel world!")

except Exception, e:
    print 'caught unhandled exception', str(e)

    os._exit(1)