llm_router.py — langchain Source File

Source Code

"""Base classes for LLM-powered router chains."""

from __future__ import annotations

from typing import Any, cast

from langchain_core._api import deprecated
from langchain_core.callbacks import (
    AsyncCallbackManagerForChainRun,
    CallbackManagerForChainRun,
)
from langchain_core.exceptions import OutputParserException
from langchain_core.language_models import BaseLanguageModel
from langchain_core.output_parsers import BaseOutputParser
from langchain_core.prompts import BasePromptTemplate
from langchain_core.utils.json import parse_and_check_json_markdown
from pydantic import model_validator
from typing_extensions import Self, override

from langchain_classic.chains import LLMChain
from langchain_classic.chains.router.base import RouterChain


@deprecated(
    since="0.2.12",
    removal="1.0",
    message=(
        "Use RunnableLambda to select from multiple prompt templates. See example "
        "in API reference: "
        "https://api.python.langchain.com/en/latest/chains/langchain.chains.router.llm_router.LLMRouterChain.html"
    ),
)
class LLMRouterChain(RouterChain):
    """A router chain that uses an LLM chain to perform routing.

    This class is deprecated. See below for a replacement, which offers several
    benefits, including streaming and batch support.

    Below is an example implementation:

        ```python
        from operator import itemgetter
        from typing import Literal
        from typing_extensions import TypedDict

        from langchain_core.output_parsers import StrOutputParser
        from langchain_core.prompts import ChatPromptTemplate
        from langchain_core.runnables import RunnableLambda, RunnablePassthrough
        from langchain_openai import ChatOpenAI

        model = ChatOpenAI(model="gpt-4o-mini")

        prompt_1 = ChatPromptTemplate.from_messages(
            [
                ("system", "You are an expert on animals."),
                ("human", "{query}"),
            ]
        )
        prompt_2 = ChatPromptTemplate.from_messages(
            [
// ... (137 more lines)