Conversation With History

• Author: 3dkids, Joonha Jeon

• Peer Review : Teddy Lee, Shinar12, Kenny Jung, Sunyoung Park (architectyou)

• Proofread : Juni Lee

• This is a part of LangChain Open Tutorial

Overview

This tutorial covers how to create a multi-turn Chain that remembers previous conversations, using LangChain. It includes managing conversation history, defining a ChatPromptTemplate, and utilizing an LLM for chain creation. The conversation history is managed using chat_history.

Table of Contents

• Overview

• Environment Setup

• Creating a Chain that Remembers Previous Conversations

• Creating a Chain to Record Conversations

References

• LangChain: MessagesPlaceholder

• LangChain: chatmessagehistory

• LangChain: runnablewithmessagehistory

---

Environment Setup

Set up the environment. You may refer to Environment Setup for more details.

[Note]

• langchain-opentutorial is a package that provides a set of easy-to-use environment setup, useful functions and utilities for tutorials.

• You can checkout the langchain-opentutorial for more details.

%%capture --no-stderr
%pip install langchain-opentutorial

# Install required packages
from langchain_opentutorial import package

package.install(
    ["langchain_core", "langchain_community", "langchain_openai"],
    verbose=False,
    upgrade=False,
)

# Set environment variables
from langchain_opentutorial import set_env

set_env(
    {
        "OPENAI_API_KEY": "",
        "LANGCHAIN_API_KEY": "",
        "LANGCHAIN_TRACING_V2": "true",
        "LANGCHAIN_ENDPOINT": "https://api.smith.langchain.com",
        "LANGCHAIN_PROJECT": "ConversationWithHistory",
    }
)

Environment variables have been set successfully.

Alternatively, environment variables can also be set using a .env file.

[Note]

• This is not necessary if you've already set the environment variables in the previous step.

from dotenv import load_dotenv

load_dotenv()

Creating a Chain that Remembers Previous Conversations

MessagesPlaceholder is a class in LangChain used to handle conversation history. It is primarily utilized in chatbots or multi-turn conversation systems to store and reuse previous conversation content.

Key Roles

Inserting Conversation History :

• Used to insert prior conversations (e.g., question-and-answer history) into the prompt.

• This allows the model to understand the context of the conversation and generate appropriate responses.

Managing Variables :

• Manages conversation history within the prompt using a specific key (e.g., chat_history).

• It is linked to a user-defined variable name.

Usage

MessagesPlaceholder(variable_name="chat_history")

• Here, chat_history is the variable name where conversation history is stored.

• As the conversation progresses, chat_history is continually updated with pairs of questions and responses.

from langchain_core.prompts import ChatPromptTemplate, MessagesPlaceholder
from langchain_community.chat_message_histories import ChatMessageHistory
from langchain_core.chat_history import BaseChatMessageHistory
from langchain_core.runnables.history import RunnableWithMessageHistory
from langchain_openai import ChatOpenAI
from langchain_core.output_parsers import StrOutputParser


# Define the prompt.
prompt = ChatPromptTemplate.from_messages(
    [
        (
            "system",
            "You are a Question-Answering chatbot. Please provide answers to the given questions.",
        ),
        # Use "chat_history" as the key for conversation history without modifying it if possible.
        MessagesPlaceholder(variable_name="chat_history"),
        ("human", "#Question:\n{question}"),  # Use user input as a variable.
    ]
)

# Create the LLM.
llm = ChatOpenAI(model_name="gpt-4o")

# Create a basic chain.
chain = prompt | llm | StrOutputParser()

Creating a Chain to Record Conversations (chain_with_history)

In this step, we create a system that manages session-based conversation history and generates an executable chain.

• Conversation History Management : The store dictionary saves and retrieves conversation history (ChatMessageHistory) by session ID. If a session does not exist, a new one is created.

• Chain Execution : RunnableWithMessageHistory combines conversation history and the chain to generate responses based on user questions and conversation history. This structure is designed to effectively manage multi-turn conversations.

# A dictionary to store session history.
store = {}


# A function to retrieve session history based on the session ID.
def get_session_history(session_ids):
    print(f"[Conversation session ID]: {session_ids}")
    if session_ids not in store:  # When the session ID is not in the store.
        # Create a new ChatMessageHistory object and save it in the store.
        store[session_ids] = ChatMessageHistory()
    return store[session_ids]  # Return the session history for the given session ID.

chain_with_history = RunnableWithMessageHistory(
    chain,
    get_session_history,  # A function to retrieve session history.
    input_messages_key="question",  # The key where the user's question will be inserted into the template variable.
    history_messages_key="chat_history",  # The key for the message in the history.
)

Execute the first question.

chain_with_history.invoke(
    # Question input.
    {"question": "My name is Teddy."},
    # Record conversations based on the session ID.
    config={"configurable": {"session_id": "abc123"}},
)

[Conversation session ID]: abc123

"Hello, Teddy! Do you have a question or something specific you'd like to discuss?"

Execute the next question.

chain_with_history.invoke(
    # Question input.
    {"question": "What's my name?"},
    # Record conversations based on the session ID.
    config={"configurable": {"session_id": "abc123"}},
)

[Conversation session ID]: abc123

'Your name is Teddy.'

Below is a case where a new session is created when the session_id is different.

chain_with_history.invoke(
    # Question input.
    {"question": "What's my name?"},
    # Record conversations based on the session ID.
    config={"configurable": {"session_id": "abc1234"}},
)

[Conversation session ID]: abc1234

"I'm sorry, but I don't have access to personal information about you, including your name."