Source code for airflow.example_dags.example_params_trigger_ui

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"""Example DAG demonstrating the usage DAG params to model a trigger UI with a user form.

This example DAG generates greetings to a list of provided names in selected languages in the logs.

from __future__ import annotations

import datetime
from pathlib import Path
from typing import TYPE_CHECKING

from airflow.decorators import task
from airflow.models.dag import DAG
from airflow.models.param import Param
from airflow.utils.trigger_rule import TriggerRule

    from airflow.models.dagrun import DagRun
    from airflow.models.taskinstance import TaskInstance

with DAG(
    dag_display_name="Params Trigger UI",
    start_date=datetime.datetime(2022, 3, 4),
    tags=["example", "params"],
        "names": Param(
            ["Linda", "Martha", "Thomas"],
            description="Define the list of names for which greetings should be generated in the logs."
            " Please have one name per line.",
            title="Names to greet",
        "english": Param(True, type="boolean", title="English"),
        "german": Param(True, type="boolean", title="German (Formal)"),
        "french": Param(True, type="boolean", title="French"),
) as dag:

    @task(task_id="get_names", task_display_name="Get names")
[docs] def get_names(**kwargs) -> list[str]: ti: TaskInstance = kwargs["ti"] dag_run: DagRun = ti.dag_run if "names" not in dag_run.conf: print("Uuups, no names given, was no UI used to trigger?") return [] return dag_run.conf["names"]
@task.branch(task_id="select_languages", task_display_name="Select languages") def select_languages(**kwargs) -> list[str]: ti: TaskInstance = kwargs["ti"] dag_run: DagRun = ti.dag_run selected_languages = [] for lang in ["english", "german", "french"]: if lang in dag_run.conf and dag_run.conf[lang]: selected_languages.append(f"generate_{lang}_greeting") return selected_languages @task(task_id="generate_english_greeting", task_display_name="Generate English greeting") def generate_english_greeting(name: str) -> str: return f"Hello {name}!" @task(task_id="generate_german_greeting", task_display_name="Erzeuge Deutsche Begrüßung") def generate_german_greeting(name: str) -> str: return f"Sehr geehrter Herr/Frau {name}." @task(task_id="generate_french_greeting", task_display_name="Produire un message d'accueil en français") def generate_french_greeting(name: str) -> str: return f"Bonjour {name}!" @task(task_id="print_greetings", task_display_name="Print greetings", trigger_rule=TriggerRule.ALL_DONE) def print_greetings(greetings1, greetings2, greetings3) -> None: for g in greetings1 or []: print(g) for g in greetings2 or []: print(g) for g in greetings3 or []: print(g) if not (greetings1 or greetings2 or greetings3): print("sad, nobody to greet :-(") lang_select = select_languages() names = get_names() english_greetings = generate_english_greeting.expand(name=names) german_greetings = generate_german_greeting.expand(name=names) french_greetings = generate_french_greeting.expand(name=names) lang_select >> [english_greetings, german_greetings, french_greetings] results_print = print_greetings(english_greetings, german_greetings, french_greetings)

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