app.py

import os
from typing import List
from langchain.embeddings.openai import OpenAIEmbeddings
from langchain.vectorstores.pinecone import Pinecone
from langchain.chains import ConversationalRetrievalChain
from langchain.chat_models import ChatOpenAI
from langchain.memory import ChatMessageHistory, ConversationBufferMemory
from langchain.docstore.document import Document
import pinecone
import chainlit as cl

pinecone.init(
    api_key=os.environ.get("PINECONE_API_KEY"),
    environment=os.environ.get("PINECONE_ENV"),
)


index_name = "langchain-demo"
embeddings = OpenAIEmbeddings()

welcome_message = "Welcome to the Chainlit Pinecone demo! Ask anything about Shakespeare's King Lear vectorized documents from Pinecone DB."


@cl.on_chat_start
async def start():
    await cl.Message(content=welcome_message).send()
    docsearch = Pinecone.from_existing_index(
        index_name=index_name, embedding=embeddings
        )

    message_history = ChatMessageHistory()

    memory = ConversationBufferMemory(
        memory_key="chat_history",
        output_key="answer",
        chat_memory=message_history,
        return_messages=True,
    )

    chain = ConversationalRetrievalChain.from_llm(
        ChatOpenAI(
            model_name="gpt-3.5-turbo", 
            temperature=0,
            streaming=True),
        chain_type="stuff",
        retriever=docsearch.as_retriever(search_kwargs={'k': 3}), # I only want maximum of three document back with the highest similarity score        
        memory=memory,
        return_source_documents=True,
    )
    cl.user_session.set("chain", chain)


@cl.on_message
async def main(message: cl.Message):
    chain = cl.user_session.get("chain")  # type: ConversationalRetrievalChain

    cb = cl.AsyncLangchainCallbackHandler()

    res = await chain.acall(message.content, callbacks=[cb])
    answer = res["answer"]
    source_documents = res["source_documents"]  # type: List[Document]

    text_elements = []  # type: List[cl.Text]

    if source_documents:
        for source_idx, source_doc in enumerate(source_documents):
            source_name = f"source_{source_idx}"
            # Create the text element referenced in the message
            text_elements.append(
                cl.Text(content=source_doc.page_content, name=source_name)
            )
        source_names = [text_el.name for text_el in text_elements]

        if source_names:
            answer += f"\nSources: {', '.join(source_names)}"
        else:
            answer += "\nNo sources found"

    await cl.Message(content=answer, elements=text_elements).send()