Re: [Twisted-Python] Callbacks, Looping, and Variable Binding

Aug. 1, 2003


      On Thu, Jul 31, 2003 at 02:20:24PM -0600, Justin Johnson wrote:
...
for item in list:
         d.addCallbacks(onSuccess, log.err, callbackArgs=(item,))
         deferreds.append(d)
and then defining onSuccess like...
def onSuccess(results, args):
        item = args[0]
        d = item.doSomethingElseThatReturnsDeferred()
        return d
Is this an acceptable way to accomplish this?  It is working in my code
but I'd like to do things the right way.
Yes. I'd make that prettier with

    def onSuccess(results, item):
        d = item.doSomethingElseThatReturnsDeferred()
        return d
...
    for item in list:
	d.addCallback(onSuccess, item)
	d.addErrback(log.err)
	deferreds.append(d)
...
...
Besides, you are adding the outer d to deferreds once per
  iteration. That's broken.
I'm not sure what you mean here.  I was adding my deferred to a list and
it seemed to be doing what I wanted (at least I think it was).
Your original code had
...
d = doSomethingThatReturnsDeferred()
for item in list:
        d.addCallbacks(onSuccess, log.err)
        deferreds.append(d)
Which ends up adding the _same_ d len(list) times to deferreds.

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Re: [Twisted-Python] Callbacks, Looping, and Variable Binding

Tommi Virtanen