Python Airflow-从PythonOperator返回结果 [英] Python Airflow - Return result from PythonOperator

问题描述

我写了一个包含多个PythonOperator的DAG

I have written a DAG with multiple PythonOperators

task1 = af_op.PythonOperator(task_id='Data_Extraction_Environment',
                          provide_context=True,
                          python_callable=Task1, dag=dag1)

def Task1(**kwargs):
    return(kwargs['dag_run'].conf.get('file'))

从PythonOperator中，我正在调用 Task1方法。该方法正在返回一个值，该值需要传递给下一个PythonOperator。如何从 task1变量中获取该值，或者如何从Task1方法中返回该值？

From PythonOperator i am calling "Task1" method. That method is returning a value,that value i need to pass to the next PythonOperator.How can i get the value from the "task1" variable or How can i get the value which is returned from Task1 method?

已更新：

    def Task1(**kwargs):
          file_name = kwargs['dag_run'].conf.get[file]
          task_instance = kwargs['task_instance']
          task_instance.xcom_push(key='file', value=file_name) 
          return file_name

  t1 = PythonOperator(task_id = 'Task1',provide_context=True,python_callable=Task1,dag=dag)

  t2 =   BashOperator(
      task_id='Moving_bucket', 
      bash_command='python /home/raw.py {{ task_instance.xcom_pull(task_ids='Task1',key='file') }} ',
      dag=dag,
    )

t2.set_upstream(t1)

推荐答案

您可能想查看Airflow的XCOM： https://airflow.apache.org/concepts.html#xcoms

You might want to check out Airflow's XCOM: https://airflow.apache.org/concepts.html#xcoms

如果您从函数返回值，则此值存储在xcom中。在您的情况下，您可以从其他Python代码中访问它：

If you return a value from a function, this value is stored in xcom. In your case, you could access it like so from other Python code:

task_instance = kwargs['task_instance']
task_instance.xcom_pull(task_ids='Task1')

或在如下模板中：

{{ task_instance.xcom_pull(task_ids='Task1') }}

如果要指定键，则可以推入XCOM（在任务内部）：

If you want to specify a key you can push into XCOM (being inside a task):

task_instance = kwargs['task_instance']
task_instance.xcom_push(key='the_key', value=my_str)

然后稍后您可以像这样访问它：

Then later on you can access it like so:

task_instance.xcom_pull(task_ids='my_task', key='the_key')

编辑1

后续问题：我不像在其他函数中使用值那样，如何将值传递给另一个PythonOperator，例如- t2 = BashOperator（task_id = 'Moving_bucket'，bash_command ='python /home/raw.py％s' ％file_name，dag = dag）-我想访问 Task1返回的file_name。

首先，在我看来，价值实际上不是 被传递给另一个 PythonOperator 但传递给 BashOperator 。

First of all, it seems to me that the value is, in fact, not being passed to another PythonOperator but to a BashOperator.

第二，这已经在上面的答案中涵盖了。字段 bash_command 是模板化的（请参见源中的 template_fields ： https://github.com/apache/incubator-airflow/blob/master/airflow/operators/bash_operator.py ）。因此，我们可以使用模板化版本：

Secondly, this is already covered in my answer above. The field bash_command is templated (see template_fields in the source: https://github.com/apache/incubator-airflow/blob/master/airflow/operators/bash_operator.py). Hence, we can use the templated version:

BashOperator(
  task_id='Moving_bucket', 
  bash_command='python /home/raw.py {{ task_instance.xcom_pull(task_ids='Task1') }} ',
  dag=dag,
)

编辑2

说明：
气流的作用类似于此：它将执行Task1，然后填充xcom，然后执行下一个任务。因此，要使您的示例正常工作，您需要先执行Task1，然后在Task1的下游执行Moving_bucket。

Explanation: Airflow works like this: It will execute Task1, then populate xcom and then execute the next task. So for your example to work you need Task1 executed first and then execute Moving_bucket downstream of Task1.

由于使用的是返回函数，因此您也可以从<$ c中省略 key ='file' $ c> xcom_pull ，而不是在函数中手动设置。

Since you are using a return function, you could also omit the key='file' from xcom_pull and not manually set it in the function.

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