问云服务器是否自带公网ip地址？

class delegate(object):

    def __init__(self, func):
        self.callbacks = []
        self.basefunc = func

    def __iadd__(self, func):
        if callable(func):
            self.__isub__(func)
            self.callbacks.append(func)
        return self

    def callback(self, func):
        if callable(func):
            self.__isub__(func)
            self.callbacks.append(func)
        return func

    def __isub__(self, func):
        try:
            self.callbacks.remove(func)
        except ValueError:
            pass
        return self

    def __call__(self, *args, **kwargs):
        result = self.basefunc(*args, **kwargs)
        for func in self.callbacks:
            newresult = func(result)
            result = result if newresult is None else newresult
        return result

@delegate
def intfactory(num):
    return int(num)

@intfactory.callback
def notify(num):
    print "notify:", num

def increment(num):
    return num+1

intfactory += increment
intfactory += lambda num: num * 2

print intfactory(3)   # outputs 8

class C(object):
  _oncreate = []

  def __new__(cls):
    return reduce(lambda x, y: y(x), cls._oncreate, super(C, cls).__new__(cls))

  @classmethod
  def oncreate(cls, func):
    cls._oncreate.append(func)

c = C()
print hasattr(c, 'spew')

@C.oncreate
def spew(obj):
  obj.spew = 42
  return obj

c = C()
print c.spew