twisted.internet.defer.DeferredList(Deferred)
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DeferredList
is a tool for collecting the results of several Deferreds.
This tracks a list of Deferred
s 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 | addTimeout | Time out this Deferred by
scheduling it to be cancelled after timeout seconds. |
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 . |
Method | __iter__ | Undocumented |
Method | send | Undocumented |
Method | asFuture | Adapt a Deferred into
a asyncio.Future
which is bound to loop . |
Class Method | fromFuture | Adapt an asyncio.Future
to a 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 . |
Method | _runCallbacks | Run the chain of callbacks once a result is available. |
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 Deferred s
should not be propagated to errbacks added to the individual Deferred s
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 ) |
(internal) Callback for when one of my deferreds fires.
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.