fad9e9aeb4
Add an example how to use flow factories and prefixing to achieve effect similar to scoping, but without it. Change-Id: Ia587ad59f76a0dd477dba79c24e5f86f4b4a34ba
114 lines
3.4 KiB
Python
114 lines
3.4 KiB
Python
# -*- coding: utf-8 -*-
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# Copyright (C) 2014 Ivan Melnikov <iv at altlinux dot org>
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#
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# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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import logging
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import os
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import sys
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logging.basicConfig(level=logging.ERROR)
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top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
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os.pardir,
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os.pardir))
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sys.path.insert(0, top_dir)
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import taskflow.engines
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from taskflow.patterns import linear_flow as lf
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from taskflow import task
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# INTRO: pseudo-scoping by adding prefixes
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# Sometimes you need scoping -- e.g. for adding several
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# similar subflows to one flow to do same stuff for different
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# data. But current version of TaskFlow does not allow that
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# directly, so you have to resort to some kind of trickery.
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# One (and more or less recommended, if not the only) way of
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# solving the problem is to transform every task name, it's
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# provides and requires values -- e.g. by adding prefix to them.
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# This example shows how this could be done.
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# The example task is simple: for each specified person, fetch
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# his or her phone number from phone book and call.
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PHONE_BOOK = {
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'jim': '444',
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'joe': '555',
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'iv_m': '666',
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'josh': '777'
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}
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class FetchNumberTask(task.Task):
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"""Task that fetches number from phone book."""
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default_provides = 'number'
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def execute(self, person):
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print('Fetching number for %s.' % person)
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return PHONE_BOOK[person.lower()]
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class CallTask(task.Task):
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"""Task that calls person by number."""
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def execute(self, person, number):
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print('Calling %s %s.' % (person, number))
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# This is how it works for one person:
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simple_flow = lf.Flow('simple one').add(
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FetchNumberTask(),
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CallTask())
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print('Running simple flow:')
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taskflow.engines.run(simple_flow, store={'person': 'Josh'})
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# To call several people you'll need a factory function that will
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# make a flow with given prefix for you. We need to add prefix
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# to task names, their provides and requires values. For requires,
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# we use `rebind` argument of task constructor.
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def subflow_factory(prefix):
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def pr(what):
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return '%s-%s' % (prefix, what)
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return lf.Flow(pr('flow')).add(
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FetchNumberTask(pr('fetch'),
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provides=pr('number'),
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rebind=[pr('person')]),
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CallTask(pr('call'),
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rebind=[pr('person'), pr('number')])
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)
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def call_them_all():
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# Let's call them all. We need a flow:
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flow = lf.Flow('call-them-prefixed')
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# We'll also need to inject person names with prefixed argument
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# name to storage to satisfy task requirements.
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persons = {}
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for person in ('Jim', 'Joe', 'Josh'):
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prefix = person.lower()
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persons['%s-person' % prefix] = person
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flow.add(subflow_factory(prefix))
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taskflow.engines.run(flow, store=persons)
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print('\nCalling many people using prefixed factory:')
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call_them_all()
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