text: # -*- coding: utf-8 -*-
  
  #    Copyright (C) 2015 Yahoo! Inc. All Rights Reserved.
  #
  #    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.DEBUG)
  
  top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
                                         os.pardir,
                                         os.pardir))
  sys.path.insert(0, top_dir)
  
  from taskflow import engines
  from taskflow.listeners import logging as logging_listener
  from taskflow.patterns import linear_flow as lf
  from taskflow import task
  
  # INTRO: This example walks through a miniature workflow which will do a
  # simple echo operation; during this execution a listener is associated with
  # the engine to receive all notifications about what the flow has performed,
  # this example dumps that output to the stdout for viewing (at debug level
  # to show all the information which is possible).
  
  
  class Echo(task.Task):
      def execute(self):
          print(self.name)
  
  
  # Generate the work to be done (but don't do it yet).
  wf = lf.Flow('abc')
  wf.add(Echo('a'))
  wf.add(Echo('b'))
  wf.add(Echo('c'))
  
  # This will associate the listener with the engine (the listener
  # will automatically register for notifications with the engine and deregister
  # when the context is exited).
  e = engines.load(wf)
  with logging_listener.DynamicLoggingListener(e):
      e.run()
  