[Twisted-Python] waitForDeferred Question

Brian Granger bgranger at scu.edu
Sat Mar 11 13:24:37 EST 2006

On 3/11/06, Phil Mayers <p.mayers at imperial.ac.uk> wrote:
> Brian Granger wrote:
> > I probably should have given more details about what I am trying to
> > do.  Before I get going, I should mention that I have been using
> > Twisted heavily for 1.5 years and I have, for the most part, learned
> > to play the "Twisted Game."
> If that is the case, you really ought to have known the answer was "you
> don't" ;o)

I respectfully disagree that what I am trying to do somehow violates
the unwritten Twisted ethic.  I am not using threads and I don't have
blocking code anywhere.  When I write things like:

>>> myresult = a.computeSomethingThatUsesTwisted()

It does not really block - it only appears to block.  What I mean by
this is that is does not block execution, it only blocks the user from
starting new commands.  The full machinery of Twisted is free to
proceed while the result is pending.

I guess I think of it as a shorthand for making the callback of a
Deferred an assignment of the result to a global variable myresult. 
Everything is asynchronous.

> >
> > So here is what I am working on:
> >
> > I am developing objects (for scientific computing) that 1) use Twisted
> > to talk over the network and 2) need to be used interactively from a
> > python prompt.  This second point is really where the difficult and
> > interesting things are.
> That is not an unreasonable use-case in fact (IMHO of course).
> The sad thing is that PyCrust is wxPython so by definition AWFUL. The
> many suggestions already are correct - stop the interpreter GUI for a
> certain time (say 10ms) then if the deferred calls back, restart with
> the result else return a "backgrounded" job
> That said, possible someone can comment if this code is current:
> http://svn.twistedmatrix.com/cvs/trunk/doc/core/examples/threadedselect/blockingdemo.py
> The Manager class getDeferred method might be a start, if you can
> integrate it with the wx-style tsr.
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Brian Granger
Santa Clara University
ellisonbg at gmail.com

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