title: Using Airflow macro outside of operators
body: <p>Is there any way to use Airflow macro outside of any operators?</p>
  
  <p>For example, in the DAG I have an action:</p>
  
  <pre><code>datestamp = '{{ ds }}'
  
  print(datestamp) # prints string not the date when I run it for any date
  
  scanner = S3KeySensor(
          task_id='scanner',
          poke_interval=60,
          timeout=24 * 60 * 60,
          soft_fail=False,
          wildcard_match=True,
          bucket_key=getPath() + datestamp, #datestamp correctly replaced with execution date
          bucket_name=bucketName,
          dag=dag)
  </code></pre>
  
  <p>So when calling scanner, "ds" value gets replaced with execution date which is expected, but I want to use "ds" value in some other places. But in that case, it doesn't replace value, instead it gets entire string as "{{ ds }}". In the above example. print statement prints "{{ ds }}" not the execution date.</p>