The @after decorator

after.py

from twisted.internet.defer import Deferred
def noop(*args):
    return args

class proxy(object):

    def __init__(self, fn):
        self.defer = Deferred()
        self.fn = fn

    def __call__(self, *args, **kwargs):
        self.defer.callback(fn(*args, **kwargs))

class after(object):

    def __init__(self, step1, key=noop):
        self.step1 = step1
        self.key = key

    def __call__(self, step2):
        def step0(*args, **kwargs):
            res = proxy(step2)
            self.step1(*self.key(*args), **kwargs).addCallbacks(res, callbackArgs=args, callbackKeywords=kwargs)
            return proxy.defer
        step0.__name__ = "after(%s, %s)" % (self.step1.__name__, step2.__name__)
        return step0