TaskFlow/Inputs and Outputs
Revised on: 10/23/2013 by Harlowja
Contents
Overview
In taskflow there are multiple ways to design how your tasks/flows and engines get inputs and produce outputs. This document will help you understand what those ways are and how to use those ways to accomplish your desired taskflow usage pattern as well as include examples that show common ways of providing input and getting output.
Task & Flow Inputs and Outputs
See: Task & Flow Arguments and Results
Engine Inputs and Outputs
Storage
The storage layer is how an engine persists flow and task details.
For more in-depth design details: [[TaskFlow/Persistence|persistence].
To initially pre-populate your engine with arguments (so that dependent tasks can immediatly start running) you can directly interact with the engine load
or run
to provide these needed inputs.
The problem:
>>> from taskflow import task >>> from taskflow import engines >>> from taskflow.patterns import linear_flow as lf >>> >>> class CatTalk(task.Task): ... def execute(self, meow): ... print meow ... >>> class DogTalk(task.Task): ... def execute(self, woof): ... print woof ... >>> flo = lf.Flow("cat-dog") >>> flo.add(CatTalk(), DogTalk()) >>> engines.run(flo) Traceback (most recent call last): File "<stdin>", line 1, in <module> File "/usr/lib/python2.6/site-packages/taskflow/engines/helpers.py", line 110, in run engine.run() File "/usr/lib/python2.6/site-packages/taskflow/utils/lock_utils.py", line 51, in wrapper return f(*args, **kwargs) File "/usr/lib/python2.6/site-packages/taskflow/engines/action_engine/engine.py", line 104, in run raise exc.MissingDependencies(self._flow, sorted(missing)) taskflow.exceptions.MissingDependencies: taskflow.patterns.linear_flow.Flow: cat-dog; 2 requires ['meow', 'woof'] but no other entity produces said requirements
To solve this you would want to do the following to make your flow run smoothly:
>>> from taskflow import task >>> from taskflow import engines >>> from taskflow.patterns import linear_flow as lf >>> >>> class CatTalk(task.Task): ... def execute(self, meow): ... print meow ... >>> class DogTalk(task.Task): ... def execute(self, woof): ... print woof ... >>> flo = lf.Flow("cat-dog") >>> flo.add(CatTalk(), DogTalk()) <taskflow.patterns.linear_flow.Flow object at 0x7f730fbf1910> >>> engines.run(flo, store={'meow': 'meow', 'woof': 'woof'}) meow woof {'meow': 'meow', 'woof': 'woof'}