Updated the "Basic - Exit handler" sample (#1109)

Modernized the sample pipeline code.

samples/basic/exit_handler.py

@@ -1,5 +1,5 @@
 #!/usr/bin/env python3
-# Copyright 2018 Google LLC
+# Copyright 2019 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -14,36 +14,44 @@
 # limitations under the License.
 
 
-import kfp.dsl as dsl
+import kfp
+from kfp import dsl
+
+
+def gcs_download_op(url):
+    return dsl.ContainerOp(
+        name='GCS - Download',
+        image='google/cloud-sdk:216.0.0',
+        command=['sh', '-c'],
+        arguments=['gsutil cat $0 | tee $1', url, '/tmp/results.txt'],
+        file_outputs={
+            'data': '/tmp/results.txt',
+        }
+    )
+
+
+def echo_op(text):
+    return dsl.ContainerOp(
+        name='echo',
+        image='library/bash:4.4.23',
+        command=['sh', '-c'],
+        arguments=['echo "$0"', text]
+    )
 
 
 @dsl.pipeline(
-  name='Exit Handler',
-  description='Download a message and print it out. Exit Handler will run at the end.'
+    name='Exit Handler',
+    description='Downloads a message and prints it. The exit handler will run after the pipeline finishes (successfully or not).'
 )
 def download_and_print(url='gs://ml-pipeline-playground/shakespeare1.txt'):
-  """A sample pipeline showing exit handler."""
-
-  exit_op = dsl.ContainerOp(
-      name='finally',
-      image='library/bash:4.4.23',
-      command=['echo', 'exit!'])
+    """A sample pipeline showing exit handler."""
 
-  with dsl.ExitHandler(exit_op):
+    exit_task = echo_op('exit!')
 
-    op1 = dsl.ContainerOp(
-       name='download',
-       image='google/cloud-sdk:216.0.0',
-       command=['sh', '-c'],
-       arguments=['gsutil cat %s | tee /tmp/results.txt' % url],
-       file_outputs={'downloaded': '/tmp/results.txt'})
+    with dsl.ExitHandler(exit_task):
+        download_task = gcs_download_op(url)
+        echo_task = echo_op(download_task.output)
 
-    op2 = dsl.ContainerOp(
-       name='echo',
-       image='library/bash:4.4.23',
-       command=['sh', '-c'],
-       arguments=['echo %s' % op1.output])
 
 if __name__ == '__main__':
-  import kfp.compiler as compiler
-  compiler.Compiler().compile(download_and_print, __file__ + '.zip')
+    kfp.compiler.Compiler().compile(download_and_print, __file__ + '.zip')