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From: "Joseph L. Casale" <jcasale@activenetwerx.com>
Newsgroups: comp.lang.python
Subject: Re: Passing data across callbacks in ThreadPoolExecutor
Date: Fri, 19 Feb 2016 17:18:55 +0000
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Xref: csiph.com comp.lang.python:103207

> It's still not clear to me specifically what you're trying to do. It
> would really help if you would describe the problem in more detail.
> Here's what I think you're trying to do:
>=20
> 1) Submit a task to a ThreadPoolExecutor and get back a future.
>=20
> 2) When the task is complete, submit another task that needs the
> result of the first task to do its work.
>=20
> 3) When the chained task is complete, return the final result of the
> chained task back to whoever submitted the original task via the
> original task's future.
>=20
> The problem arises in that the original task's future already
> completed when the original task did. The chained task sets its result
> in a different future that the submitter didn't know about.

Yes, I may have 2 or more tasks that depend on the previous.
They are each distinct tasks, or continuations, so they each want the resul=
t
of the previous task however each one can cancel the set.

The callback model doesn't apply, its based on the result of _one_ task.

What I need I are continuations, much like the .NET TPL.

def task_a():
    return "a"

def task_b():
    return "b"

def task_c():
    return "c"

So I submit task_a, if it completes successfully, task_b runs on its result=
.
If task_b completes successfully, task_c runs on its result. They "look"
like callbacks, but they are continuations.

Task_b must be able to cancel the continuation of task_c  if it see's task_=
a
has failed.

Thanks for the continued help!
jlc=