twisted.internet.defer.DeferredList : API documentation

DeferredList is a tool for collecting the results of several Deferreds.

This tracks a list of Deferreds for their results, and makes a single callback when they have all completed. By default, the ultimate result is a list of (success, result) tuples, 'success' being a boolean. DeferredList exposes the same API that Deferred does, so callbacks and errbacks can be added to it in the same way.

DeferredList is implemented by adding callbacks and errbacks to each Deferred in the list passed to it. This means callbacks and errbacks added to the Deferreds before they are passed to DeferredList will change the result that DeferredList sees (i.e., DeferredList is not special). Callbacks and errbacks can also be added to the Deferreds after they are passed to DeferredList and DeferredList may change the result that they see.

See the documentation for the __init__ arguments for more information.

Method	__init__	Initialize a DeferredList.
Method	cancel	Cancel this `DeferredList`.
Instance Variable	_deferredList	The `list` of `Deferred`s to track.
Method	_cbDeferred	(internal) Callback for when one of my deferreds fires.

Inherited from Deferred:

Instance Variable	called	A flag which is `False` until either `callback` or `errback` is called and afterwards always `True`. (type: `bool`)
Instance Variable	paused	A counter of how many unmatched `pause` calls have been made on this instance. (type: `int`)
Method	addCallbacks	Add a pair of callbacks (success and error) to this `Deferred`.
Method	addCallback	Convenience method for adding just a callback.
Method	addErrback	Convenience method for adding just an errback.
Method	addBoth	Convenience method for adding a single callable as both a callback and an errback.
Method	chainDeferred	Chain another `Deferred` to this `Deferred`.
Method	callback	Run all success callbacks that have been added to this `Deferred`.
Method	errback	Run all error callbacks that have been added to this `Deferred`.
Method	pause	Stop processing on a `Deferred` until `unpause`() is called.
Method	unpause	Process all callbacks made since `pause`() was called.
Method	__str__	Return a string representation of this `Deferred`.
Instance Variable	_suppressAlreadyCalled	A flag used by the cancellation mechanism which is `True` if the Deferred has no canceller and has been cancelled, `False` otherwise. If `True`, it can be expected that `callback` or `errback` will eventually be called and the result should be silently discarded. (type: `bool`)
Instance Variable	_runningCallbacks	A flag which is `True` while this instance is executing its callback chain, used to stop recursive execution of `_runCallbacks` (type: `bool`)
Instance Variable	_chainedTo	If this Deferred is waiting for the result of another Deferred, this is a reference to the other Deferred. Otherwise, `None`.
Method	_startRunCallbacks	Undocumented
Method	_continuation	Build a tuple of callback and errback with `_continue` to be used by `_addContinue` and `_removeContinue` on another Deferred.
Method	_runCallbacks	Run the chain of callbacks once a result is available.

def __init__(self, deferredList, fireOnOneCallback=False, fireOnOneErrback=False, consumeErrors=False): (source)

overrides twisted.internet.defer.Deferred.__init__

Initialize a DeferredList.

Parameters	deferredList	The list of deferreds to track. (type: `list` of `Deferred`s)
	fireOnOneCallback	(keyword param) a flag indicating that this `DeferredList` will fire when the first `Deferred` in `deferredList` fires with a non-failure result without waiting for any of the other Deferreds. When this flag is set, the DeferredList will fire with a two-tuple: the first element is the result of the Deferred which fired; the second element is the index in `deferredList` of that Deferred. (type: `bool`)
	fireOnOneErrback	(keyword param) a flag indicating that this `DeferredList` will fire when the first `Deferred` in `deferredList` fires with a failure result without waiting for any of the other Deferreds. When this flag is set, if a Deferred in the list errbacks, the DeferredList will errback with a `FirstError` failure wrapping the failure of that Deferred. (type: `bool`)
	consumeErrors	(keyword param) a flag indicating that failures in any of the included `Deferreds` should not be propagated to errbacks added to the individual `Deferreds` after this `DeferredList` is constructed. After constructing the `DeferredList`, any errors in the individual `Deferred`s will be converted to a callback result of `None`. This is useful to prevent spurious 'Unhandled error in Deferred' messages from being logged. This does not prevent `fireOnOneErrback` from working. (type: `bool`)

def cancel(self): (source)

overrides twisted.internet.defer.Deferred.cancel

Cancel this DeferredList.

If the DeferredList hasn't fired yet, cancel every Deferred in the list.

If the DeferredList has fired, including the case where the fireOnOneCallback/fireOnOneErrback flag is set and the DeferredList fires because one Deferred in the list fires with a non-failure/failure result, do nothing in the cancel method.

t.i.d.DeferredList(Deferred) : class documentation