Updated the "Basic - Recursive loop" sample (#1113)

Modernized the sample pipeline code.

samples/basic/recursion.py

@@ -13,54 +13,57 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import kfp.dsl as dsl
 
-class FlipCoinOp(dsl.ContainerOp):
-  """Flip a coin and output heads or tails randomly."""
+import kfp
+from kfp import dsl
 
-  def __init__(self):
-    super(FlipCoinOp, self).__init__(
-        name='Flip',
+
+def flip_coin_op():
+    """Flip a coin and output heads or tails randomly."""
+    return dsl.ContainerOp(
+        name='Flip coin',
         image='python:alpine3.6',
         command=['sh', '-c'],
         arguments=['python -c "import random; result = \'heads\' if random.randint(0,1) == 0 '
-                   'else \'tails\'; print(result)" | tee /tmp/output'],
-        file_outputs={'output': '/tmp/output'})
+                  'else \'tails\'; print(result)" | tee /tmp/output'],
+        file_outputs={'output': '/tmp/output'}
+    )
 
-class PrintOp(dsl.ContainerOp):
-  """Print a message."""
 
-  def __init__(self, msg):
-    super(PrintOp, self).__init__(
+def print_op(msg):
+    """Print a message."""
+    return dsl.ContainerOp(
         name='Print',
         image='alpine:3.6',
         command=['echo', msg],
     )
 
-# Use the dsl.graph_component to decorate functions that are
+
+# Use the dsl.graph_component to decorate pipeline functions that can be
 # recursively called.
 @dsl.graph_component
 def flip_component(flip_result):
-  print_flip = PrintOp(flip_result)
-  flipA = FlipCoinOp().after(print_flip)
-  with dsl.Condition(flipA.output == 'heads'):
-    # When the flip_component is called recursively, the flipA.output
-    # from inside the graph component will be passed to the next flip_component
-    # as the input whereas the flip_result in the current graph component
-    # comes from the flipA.output in the flipcoin function.
-    flip_component(flipA.output)
+    print_flip = print_op(flip_result)
+    flipA = flip_coin_op().after(print_flip)
+    with dsl.Condition(flipA.output == 'heads'):
+        # When the flip_component is called recursively, the flipA.output
+        # from inside the graph component will be passed to the next flip_component
+        # as the input whereas the flip_result in the current graph component
+        # comes from the flipA.output in the flipcoin function.
+        flip_component(flipA.output)
+
 
 @dsl.pipeline(
-    name='pipeline flip coin',
-    description='shows how to use dsl.Condition.'
+    name='Recursive loop pipeline',
+    description='Shows how to create recursive loops.'
 )
 def flipcoin():
-  flipA = FlipCoinOp()
-  flip_loop = flip_component(flipA.output)
-  # flip_loop is a graph_component with the outputs field
-  # filled with the returned dictionary.
-  PrintOp('cool, it is over. %s' % flipA.output).after(flip_loop)
+    first_flip = flip_coin_op()
+    flip_loop = flip_component(first_flip.output)
+    # flip_loop is a graph_component with the outputs field
+    # filled with the returned dictionary.
+    print_op('cool, it is over.').after(flip_loop)
+
 
 if __name__ == '__main__':
-  import kfp.compiler as compiler
-  compiler.Compiler().compile(flipcoin, __file__ + '.tar.gz')
+    kfp.compiler.Compiler().compile(flipcoin, __file__ + '.tar.gz')