"Nathan" == Nathan <nathan.stocks@gmail.com> writes:
Nathan> I regularly use the return values of deferreds to simulate Nathan> synchronous behaviour like this: [snip] Nathan> So now I'm trying to do the same thing with DeferredList's, but Nathan> apparently the semantics aren't the same. Here's some actual Nathan> runnable sample code trying to use the DeferredList: Hi Nathan You're not using deferreds properly. In the simple/typical case, when you call a function that returns a deferred, you will want to add (at least) a callback to that deferred. The callback then gets called with the value that is being passed down the callback chain. Change your code to the below and it works. Your original code appears to work only because you're testing a deferred result in a Boolean context, which takes you to the true part of your if. You need to add call/errbacks to the deferred there too. Terry --- from twisted.internet import reactor, defer def callback_function(results): return "(--> This is the value that I want to get into retval! <--)" def make_a_list(): deferred1 = defer.Deferred() deferred2 = defer.Deferred() dl = defer.DeferredList([deferred1, deferred2]) dl.addCallback(callback_function) deferred1.callback('one') deferred2.callback('two') return dl def test(): def cb(val): print "retval is:", val make_a_list().addCallback(cb) reactor.callWhenRunning(test) reactor.callLater(2.0, reactor.stop) reactor.run()