Source code for airflow.example_dags.example_xcom

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"""Example DAG demonstrating the usage of XComs."""

from __future__ import annotations

import pendulum

from airflow.decorators import task
from airflow.models.dag import DAG
from airflow.models.xcom_arg import XComArg
from airflow.operators.bash import BashOperator

[docs]value_1 = [1, 2, 3]
[docs]value_2 = {"a": "b"}
[docs]def push(ti=None): """Pushes an XCom without a specific target""" ti.xcom_push(key="value from pusher 1", value=value_1)
[docs]def push_by_returning(): """Pushes an XCom without a specific target, just by returning it""" return value_2
def _compare_values(pulled_value, check_value): if pulled_value != check_value: raise ValueError(f"The two values differ {pulled_value} and {check_value}") @task
[docs]def puller(pulled_value_2, ti=None): """Pull all previously pushed XComs and check if the pushed values match the pulled values.""" pulled_value_1 = ti.xcom_pull(task_ids="push", key="value from pusher 1") _compare_values(pulled_value_1, value_1) _compare_values(pulled_value_2, value_2)
[docs]def pull_value_from_bash_push(ti=None): bash_pushed_via_return_value = ti.xcom_pull(key="return_value", task_ids="bash_push") bash_manually_pushed_value = ti.xcom_pull(key="manually_pushed_value", task_ids="bash_push") print(f"The xcom value pushed by task push via return value is {bash_pushed_via_return_value}") print(f"The xcom value pushed by task push manually is {bash_manually_pushed_value}")
with DAG( "example_xcom", schedule="@once", start_date=pendulum.datetime(2021, 1, 1, tz="UTC"), catchup=False, tags=["example"], ) as dag:
[docs] bash_push = BashOperator( task_id="bash_push", bash_command='echo "bash_push demo" && ' 'echo "Manually set xcom value ' '{{ ti.xcom_push(key="manually_pushed_value", value="manually_pushed_value") }}" && ' 'echo "value_by_return"', )
bash_pull = BashOperator( task_id="bash_pull", bash_command='echo "bash pull demo" && ' f'echo "The xcom pushed manually is {XComArg(bash_push, key="manually_pushed_value")}" && ' f'echo "The returned_value xcom is {XComArg(bash_push)}" && ' 'echo "finished"', do_xcom_push=False, ) python_pull_from_bash = pull_value_from_bash_push() [bash_pull, python_pull_from_bash] << bash_push puller(push_by_returning()) << push()

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