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