Example which shows how to move values from one task to another

Part of blueprint more-examples

Change-Id: I05151c3f827d6a8a0b6a7f0aeab17bab2c8ce440

doc/source/examples.rst

@@ -1,3 +1,15 @@
+Passing values from and to tasks
+================================
+
+.. note::
+
+    Full source located at :example:`simple_linear_pass`.
+
+.. literalinclude:: ../../taskflow/examples/simple_linear_pass.py
+    :language: python
+    :linenos:
+    :lines: 16-
+
 Making phone calls
 ==================
 

taskflow/examples/simple_linear_pass.out.txt

@@ -0,0 +1,9 @@
+Constructing...
+Loading...
+Compiling...
+Preparing...
+Running...
+Executing 'a'
+Executing 'b'
+Got input 'a'
+Done...

taskflow/examples/simple_linear_pass.py

@@ -0,0 +1,68 @@
+# -*- coding: utf-8 -*-
+
+#    Copyright (C) 2014 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.ERROR)
+
+self_dir = os.path.abspath(os.path.dirname(__file__))
+top_dir = os.path.abspath(os.path.join(os.path.dirname(__file__),
+                                       os.pardir,
+                                       os.pardir))
+sys.path.insert(0, top_dir)
+sys.path.insert(0, self_dir)
+
+from taskflow import engines
+from taskflow.patterns import linear_flow
+from taskflow import task
+
+# INTRO: This examples shows how a task (in a linear/serial workflow) can
+# produce an output that can be then consumed/used by a downstream task.
+
+
+class TaskA(task.Task):
+    default_provides = ['a']
+
+    def execute(self):
+        print("Executing '%s'" % (self.name))
+        return 'a'
+
+
+class TaskB(task.Task):
+    def execute(self, a):
+        print("Executing '%s'" % (self.name))
+        print("Got input '%s'" % (a))
+
+
+print("Constructing...")
+wf = linear_flow.Flow("pass-from-to")
+wf.add(TaskA('a'), TaskB('b'))
+
+print("Loading...")
+e = engines.load(wf)
+
+print("Compiling...")
+e.compile()
+
+print("Preparing...")
+e.prepare()
+
+print("Running...")
+e.run()
+
+print("Done...")