[Twisted-Python] sleeping in inlineCallbacks

Brian Granger ellisonbg.net at gmail.com
Thu Oct 29 14:38:34 EDT 2009

> Hi Brian
> Forgive me for butting in, but.... why :-)
Helpful butting in is more than fine..

> Importing the reactor is no big deal, and if you use task.deferLater, apart
> from not having to write any code you also have the advantage of being able
> to pass it a result that the deferred will be called with.
> For this reason you can also put a task.deferLater result into a callback
> chain to achieve an async sleep and it will duly pass the result along.
> E.g.:
>  from twisted.internet import reactor, task, defer
>  d = somethingReturningADeferred()
>  d.addCallback(lambda x: task.deferLater(reactor, 5.0, defer.passthru, x))
Ahh, I see.  I saw the signature of deferLater and the Clock class in task
and I thought that I would have
to create a Clock instance by hand.  That I can simply use the reactor
(which of course is already imported and running in my code) simplifies the
usage of deferLater.  Thanks!

But, even with this, I do like the flow and readability of code that uses
sleep like this:

def f():
  result1 = yield somethingDeferred()
  yield sleep(1.0)
  result2 = yield anotherDeferred(result2)

Rather than the way that deferLater looks:

def f():
  result1 = yield somethingDeferred()
  result2 = yield task.deferLater(reactor, 1.0, anotherDeferred, result2)

But, the difference at this point is entirely aesthetic.

One question though - can someone explain the need/usage cases for
task.Clock and the other things in task?



> Terry
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