[Twisted-Python] Waiting for multiple events

Itamar Shtull-Trauring twisted at itamarst.org
Wed Feb 20 06:47:07 EST 2002

Andrew Bennetts wrote:

> I have a collection of Deferreds.  When they all complete, I want to trigger
> a "all complete" callback (probably via a Deferred).  Alternatively, upon an
> error from any of the callbacks, I want to trigger the errback of that
> "all complete" Deferred.
> Is there something already written to do this?  Or do I need to write it
> myself?

# this code is untested

class WaitForCallbacks:

    def __init__(self, count, finishedDeferred):
        self.count = count
        self.callbacks = 0
        self.finishedDeferred = finishedDeferred

    def callback(self, result):
        self.callbacks = self.callbacks + 1
        if self.callbacks == self.count:
        return result

    def errback(self, err):

# then you make an instance of this class:
o = WaitForCallbacks(5, allComplete)

# any deferred D we want to connect, we do:
D.addCallbacks(o.callback, o.errback)

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