What to do when we want to send a Slack notification telling us how many values have we processed in our DAG? I suggest doing it like this:

• First, we have to store the value in the XCom. We can do it by returning the value from the PythonOperator. In this case, Airflow will automatically store it in XCom using the return_value as the key.

• In the following step, we can define a SlackAPIPostOperator that uses a template to retrieve the value from XCom and puts it in the message sent to a Slack channel:

```python from airflow.operators.slack_operator import SlackAPIPostOperator

send_to_slack = SlackAPIPostOperator( task_id=’notify_slack’, channel=’#airflow’, username=’Airflow’, text=”DAG run {{ execution_date }} processed {{ task_instance.xcom_pull(‘other_task’, key=’return_value’) }} values.” slack_conn_id=’slack_connection_id’ )