[GitHub] Fokko closed pull request #4365: [AIRFLOW-1684] - Branching based on XCom variable (Docs)

[GitBox <gi...@apache.org>]

Fokko closed pull request #4365: [AIRFLOW-1684] - Branching based on XCom variable (Docs)
URL: https://github.com/apache/incubator-airflow/pull/4365
 
 
   

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diff --git a/docs/concepts.rst b/docs/concepts.rst
index eac7a8a7f1..766b69b783 100644
--- a/docs/concepts.rst
+++ b/docs/concepts.rst
@@ -522,6 +522,37 @@ Not like this, where the join task is skipped
 
 .. image:: img/branch_bad.png
 
+The ``BranchPythonOperator`` can also be used with XComs allowing branching
+context to dynamically decide what branch to follow based on previous tasks.
+For example:
+
+.. code:: python
+
+  def branch_func(**kwargs):
+      ti = kwargs['ti']
+      xcom_value = int(ti.xcom_pull(task_ids='start_task'))
+      if xcom_value >= 5:
+          return 'continue_task'
+      else:
+          return 'stop_task'
+
+  start_op = BashOperator(
+      task_id='start_task',
+      bash_command="echo 5",
+      xcom_push=True,
+      dag=dag)
+
+  branch_op = BranchPythonOperator(
+      task_id='branch_task',
+      provide_context=True,
+      python_callable=branch_func,
+      dag=dag)
+
+  continue_op = DummyOperator(task_id='continue_task', dag=dag)
+  stop_op = DummyOperator(task_id='stop_task', dag=dag)
+
+  start_op >> branch_op >> [continue_op, stop_op]
+
 SubDAGs
 =======
 


 

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