CODEWITHSUNDEEP
pythonpy-langchainollama
Elwebman Amsterdam
Elwebman Amsterdam

Reputation: 21

How to add chat history to RAG using langchain

I have created a python app where I am storing some documents (pdf, url ) using langchain chroma db. I then retrieve this data and start ask questions and get response from a locally stored AI. I was able to add chat history when using ChatPromptTemplate.from_messages. On the below however I do not know where to add the chat history when using ChatPromptTemplate.from_template.

after_rag_template = """You are an respectful and honest assistant. You have to answer the user's \
questions using only the context provided to you. If you don't know the answer, \
just say you don't know. Don't try to make up an answer.:
{context}
Question: {question}
"""
after_rag_prompt = ChatPromptTemplate.from_template(after_rag_template)
after_rag_chain = (
{"context": retriever, "question": RunnablePassthrough()}
| after_rag_prompt
| model_local
| StrOutputParser()
)
content = after_rag_chain.invoke(prompt)

Upvotes: 1

Views: 336

Answers (1)

Pythoner
Pythoner

Reputation: 640

There are a few pieces of documentation both internally on the LangChain site as well as other tutorial websites like DevNavigator you rely on to solve this, but its essentially done in a few simple steps:

  1. Define Prompt Template: Create a template with placeholders for {chat_history}, {context}, and {question}. You can use the template class in the links I cited above.

  2. Format Chat History: Convert a list of HumanMessage and AIMessage objects into a formatted string for insertion into the prompt.

  3. Build RAG Chain: Use a retriever to fetch relevant context. Pass chat_history and question into the chain. Use a language model to generate responses.

  4. Invoke the Chain: Provide the user’s query and the formatted chat history as inputs when calling the chain.

  5. Manage Chat History Statefully: Use LangChain's ConversationBufferMemory to maintain chat history across interactions. Check out the documentation cited above to learn more.

Upvotes: 1

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