Source code for airflow.operators.branch

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"""Branching operators."""

from __future__ import annotations

from typing import TYPE_CHECKING, Iterable

from airflow.models.baseoperator import BaseOperator
from airflow.models.skipmixin import SkipMixin

if TYPE_CHECKING:
    from airflow.utils.context import Context


[docs]class BranchMixIn(SkipMixin):
    """Utility helper which handles the branching as one-liner."""

[docs]    def do_branch(self, context: Context, branches_to_execute: str | Iterable[str]) -> str | Iterable[str]:
        """Implement the handling of branching including logging."""
        self.log.info("Branch into %s", branches_to_execute)
        self.skip_all_except(context["ti"], branches_to_execute)
        return branches_to_execute


[docs]class BaseBranchOperator(BaseOperator, BranchMixIn):
    """
    A base class for creating operators with branching functionality, like to BranchPythonOperator.

    Users should create a subclass from this operator and implement the function
    `choose_branch(self, context)`. This should run whatever business logic
    is needed to determine the branch, and return either the task_id for
    a single task (as a str) or a list of task_ids.

    The operator will continue with the returned task_id(s), and all other
    tasks directly downstream of this operator will be skipped.
    """

[docs]    def choose_branch(self, context: Context) -> str | Iterable[str]:
        """
        Abstract method to choose which branch to run.

        Subclasses should implement this, running whatever logic is
        necessary to choose a branch and returning a task_id or list of
        task_ids.

        :param context: Context dictionary as passed to execute()
        """
        raise NotImplementedError

[docs]    def execute(self, context: Context):
        return self.do_branch(context, self.choose_branch(context))