branch.py — langchain Source File

Source Code

"""Runnable that selects which branch to run based on a condition."""

from collections.abc import (
    AsyncIterator,
    Awaitable,
    Callable,
    Iterator,
    Mapping,
    Sequence,
)
from typing import (
    Any,
    cast,
)

from pydantic import BaseModel, ConfigDict
from typing_extensions import override

from langchain_core.runnables.base import (
    Runnable,
    RunnableLike,
    RunnableSerializable,
    coerce_to_runnable,
)
from langchain_core.runnables.config import (
    RunnableConfig,
    ensure_config,
    get_async_callback_manager_for_config,
    get_callback_manager_for_config,
    patch_config,
)
from langchain_core.runnables.utils import (
    ConfigurableFieldSpec,
    Input,
    Output,
    get_unique_config_specs,
)

_MIN_BRANCHES = 2


class RunnableBranch(RunnableSerializable[Input, Output]):
    """`Runnable` that selects which branch to run based on a condition.

    The `Runnable` is initialized with a list of `(condition, Runnable)` pairs and
    a default branch.

    When operating on an input, the first condition that evaluates to True is
    selected, and the corresponding `Runnable` is run on the input.

    If no condition evaluates to `True`, the default branch is run on the input.

    Examples:
        ```python
        from langchain_core.runnables import RunnableBranch

        branch = RunnableBranch(
            (lambda x: isinstance(x, str), lambda x: x.upper()),
            (lambda x: isinstance(x, int), lambda x: x + 1),
            (lambda x: isinstance(x, float), lambda x: x * 2),
// ... (402 more lines)