title: Macros in the Airflow Python operator
body: <p>Can I use macros with the PythonOperator? I tried following, but I was unable to get the macros rendered:</p>
  
  <pre><code>dag = DAG(
      'temp',
      default_args=default_args,
      description='temp dag',
      schedule_interval=timedelta(days=1))
  
  def temp_def(a, b, **kwargs):
      print '{{ds}}'
      print '{{execution_date}}'
      print 'a=%s, b=%s, kwargs=%s' % (str(a), str(b), str(kwargs))
  
  ds = '{{ ds }}'
  mm = '{{ execution_date }}'
  
  t1 = PythonOperator(
      task_id='temp_task',
      python_callable=temp_def,
      op_args=[mm , ds],
      provide_context=False,
      dag=dag)
  </code></pre>