On Mon, May 26, 2003 at 04:50:58PM +1000, Stuart Hungerford wrote:

I'd like to make use of the very neat DeferredList and also the utility function getProcessOutput(). My understanding is that getProcessOutput() returns a Deferred that returns a string of the process output.

Your understanding is correct.

Are there any issues with passing a list of getProcessOutput() results to a DeferredList? I understand the DeferredList still needs its own callback registered for completion of the list of deferreds.

There's nothing special going on. As far as a DeferredList is concerned, all Deferreds are the same. Where the Deferred comes from is irrelevant.

My initial tests with this setup just seem to suspend and not return, which is almost certainly something I've misunderstood in using Deferreds.

I suspect you're right, you probably are misunderstanding something. It's hard to say what, though, without more information. (But when something is mysteriously freezing, it's hard to know what information to give!) A DeferredList, by default, calls its callbacks *only when all of its Deferreds have fired*. (If some of the Deferreds fail, that's ok, just so long as they all call their callback/errback at some point). A DeferredList has no way of reporting partial results. I'm going to guess what your problem might be, based on a problem I once had. :) If you have multiple Deferreds, some "depend" on others, DeferredList's default behaviour isn't what you want. By "depend" I mean if Deferred A fails (and so fires its errback, not callback), then Deferred B will never be called, i.e. B depends on A. (This is not official terminology! :). In that case, you probably want to use the fireOnOneErrback flag of DeferredList. This changes the behaviour of DeferredList so that it will fire its callbacks as soon as either: - All its Deferreds have fired their callbacks, or - any of its Deferreds have fired an errback. Does any of this help you? -Andrew.