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Package twisted :: Package internet :: Module defer :: Class Deferred
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Class Deferred

Known Subclasses:
CancelableDeferred

This is a callback which will be put off until later.

Why do we want this? Well, in cases where a function in a threaded program would block until it gets a result, for Twisted it should not block. Instead, it should return a Deferred.

This can be implemented for protocols that run over the network by writing an asynchronous protocol for twisted.internet. For methods that come from outside packages that are not under our control, we use threads (see for example twisted.enterprise.adbapi).

For more information about Deferreds, see doc/howto/defer.html or http://twistedmatrix.com/projects/core/documentation/howto/defer.html
Method Summary
  __init__(self)
  __repr__(self)
  __str__(self)
  addBoth(self, callback, *args, **kw)
Convenience method for adding a single callable as both a callback and an errback.
  addCallback(self, callback, *args, **kw)
Convenience method for adding just a callback.
  addCallbacks(self, callback, errback, callbackArgs, callbackKeywords, errbackArgs, errbackKeywords)
Add a pair of callbacks (success and error) to this Deferred.
  addErrback(self, errback, *args, **kw)
Convenience method for adding just an errback.
  callback(self, result)
Run all success callbacks that have been added to this Deferred.
  chainDeferred(self, d)
Chain another Deferred to this Deferred.
  errback(self, fail)
Run all error callbacks that have been added to this Deferred.
  pause(self)
Stop processing on a Deferred until unpause() is called.
  setTimeout(self, seconds, timeoutFunc, *args, **kw)
Set a timeout function to be triggered if I am not called.
  unpause(self)
Process all callbacks made since pause() was called.

Class Variable Summary
Implements __implemented__ = <implementedBy twisted.internet.defer....
ClassProvides __providedBy__ = <zope.interface.declarations.ClassProvi...
ClassProvides __provides__ = <zope.interface.declarations.ClassProvide...
int called = 0                                                                     
bool debug = False
int paused = 0                                                                     
NoneType timeoutCall = None                                                                  

Method Details

addBoth(self, callback, *args, **kw)

Convenience method for adding a single callable as both a callback and an errback.

See addCallbacks.

addCallback(self, callback, *args, **kw)

Convenience method for adding just a callback.

See addCallbacks.

addCallbacks(self, callback, errback=None, callbackArgs=None, callbackKeywords=None, errbackArgs=None, errbackKeywords=None)

Add a pair of callbacks (success and error) to this Deferred.

These will be executed when the 'master' callback is run.

addErrback(self, errback, *args, **kw)

Convenience method for adding just an errback.

See addCallbacks.

callback(self, result)

Run all success callbacks that have been added to this Deferred.

Each callback will have its result passed as the first argument to the next; this way, the callbacks act as a 'processing chain'. Also, if the success-callback returns a Failure or raises an Exception, processing will continue on the *error*- callback chain.

chainDeferred(self, d)

Chain another Deferred to this Deferred.

This method adds callbacks to this Deferred to call d's callback or errback, as appropriate.

errback(self, fail=None)

Run all error callbacks that have been added to this Deferred.

Each callback will have its result passed as the first argument to the next; this way, the callbacks act as a 'processing chain'. Also, if the error-callback returns a non-Failure or doesn't raise an Exception, processing will continue on the *success*-callback chain.

If the argument that's passed to me is not a failure.Failure instance, it will be embedded in one. If no argument is passed, a failure.Failure instance will be created based on the current traceback stack.

Passing a string as `fail' is deprecated, and will be punished with a warning message.

pause(self)

Stop processing on a Deferred until unpause() is called.

setTimeout(self, seconds, timeoutFunc=<function timeout at 0x404da374>, *args, **kw)

Set a timeout function to be triggered if I am not called.
Parameters:
seconds - How long to wait (from now) before firing the timeoutFunc.
timeoutFunc - will receive the Deferred and *args, **kw as its arguments. The default timeoutFunc will call the errback with a TimeoutError.

unpause(self)

Process all callbacks made since pause() was called.

Class Variable Details

__implemented__

Type:
Implements
Value:
<implementedBy twisted.internet.defer.Deferred>

__providedBy__

Type:
ClassProvides
Value:
<zope.interface.declarations.ClassProvides object at 0x413ae52c>

__provides__

Type:
ClassProvides
Value:
<zope.interface.declarations.ClassProvides object at 0x413ae52c>

called

Type:
int
Value:
0                                                                     

debug

Type:
bool
Value:
False

paused

Type:
int
Value:
0                                                                     

timeoutCall

Type:
NoneType
Value:
None                                                                  

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