base.py — langchain Source File

Source Code

"""Chain that carries on a conversation and calls an LLM."""

from langchain_core._api import deprecated
from langchain_core.prompts import BasePromptTemplate
from pydantic import ConfigDict, Field, model_validator
from typing_extensions import Self, override

from langchain_classic.base_memory import BaseMemory
from langchain_classic.chains.conversation.prompt import PROMPT
from langchain_classic.chains.llm import LLMChain
from langchain_classic.memory.buffer import ConversationBufferMemory


@deprecated(
    since="0.2.7",
    alternative="langchain_core.runnables.history.RunnableWithMessageHistory",
    removal="1.0",
)
class ConversationChain(LLMChain):
    """Chain to have a conversation and load context from memory.

    This class is deprecated in favor of `RunnableWithMessageHistory`. Please refer
    to this tutorial for more detail: https://python.langchain.com/docs/tutorials/chatbot/

    `RunnableWithMessageHistory` offers several benefits, including:

    - Stream, batch, and async support;
    - More flexible memory handling, including the ability to manage memory
        outside the chain;
    - Support for multiple threads.

    Below is a minimal implementation, analogous to using `ConversationChain` with
    the default `ConversationBufferMemory`:

        ```python
        from langchain_core.chat_history import InMemoryChatMessageHistory
        from langchain_core.runnables.history import RunnableWithMessageHistory
        from langchain_openai import ChatOpenAI


        store = {}  # memory is maintained outside the chain


        def get_session_history(session_id: str) -> InMemoryChatMessageHistory:
            if session_id not in store:
                store[session_id] = InMemoryChatMessageHistory()
            return store[session_id]


        model = ChatOpenAI(model="gpt-3.5-turbo-0125")

        chain = RunnableWithMessageHistory(model, get_session_history)
        chain.invoke(
            "Hi I'm Bob.",
            config={"configurable": {"session_id": "1"}},
        )  # session_id determines thread
        ```

    Memory objects can also be incorporated into the `get_session_history` callable:

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