```python from langchain.embeddings.openai import OpenAIEmbeddings from langchain.vectorstores import Chroma from langchain.text_splitter import CharacterTextSplitter from langchain.llms import OpenAI from langchain.chains import ConversationalRetrievalChain ``` Load in documents. You can replace this with a loader for whatever type of data you want ```python from langchain.document_loaders import TextLoader loader = TextLoader("../../state_of_the_union.txt") documents = loader.load() ``` If you had multiple loaders that you wanted to combine, you do something like: ```python # loaders = [....] # docs = [] # for loader in loaders: # docs.extend(loader.load()) ``` We now split the documents, create embeddings for them, and put them in a vectorstore. This allows us to do semantic search over them. ```python text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0) documents = text_splitter.split_documents(documents) embeddings = OpenAIEmbeddings() vectorstore = Chroma.from_documents(documents, embeddings) ``` ``` Using embedded DuckDB without persistence: data will be transient ``` We can now create a memory object, which is necessary to track the inputs/outputs and hold a conversation. ```python from langchain.memory import ConversationBufferMemory memory = ConversationBufferMemory(memory_key="chat_history", return_messages=True) ``` We now initialize the `ConversationalRetrievalChain` ```python qa = ConversationalRetrievalChain.from_llm(OpenAI(temperature=0), vectorstore.as_retriever(), memory=memory) ``` ```python query = "What did the president say about Ketanji Brown Jackson" result = qa({"question": query}) ``` ```python result["answer"] ``` ``` " The president said that Ketanji Brown Jackson is one of the nation's top legal minds, a former top litigator in private practice, a former federal public defender, and from a family of public school educators and police officers. He also said that she is a consensus builder and has received a broad range of support from the Fraternal Order of Police to former judges appointed by Democrats and Republicans." ``` ```python query = "Did he mention who she succeeded" result = qa({"question": query}) ``` ```python result['answer'] ``` ``` ' Ketanji Brown Jackson succeeded Justice Stephen Breyer on the United States Supreme Court.' ``` ## Pass in chat history In the above example, we used a Memory object to track chat history. We can also just pass it in explicitly. In order to do this, we need to initialize a chain without any memory object. ```python qa = ConversationalRetrievalChain.from_llm(OpenAI(temperature=0), vectorstore.as_retriever()) ``` Here's an example of asking a question with no chat history ```python chat_history = [] query = "What did the president say about Ketanji Brown Jackson" result = qa({"question": query, "chat_history": chat_history}) ``` ```python result["answer"] ``` ``` " The president said that Ketanji Brown Jackson is one of the nation's top legal minds, a former top litigator in private practice, a former federal public defender, and from a family of public school educators and police officers. He also said that she is a consensus builder and has received a broad range of support from the Fraternal Order of Police to former judges appointed by Democrats and Republicans." ``` Here's an example of asking a question with some chat history ```python chat_history = [(query, result["answer"])] query = "Did he mention who she succeeded" result = qa({"question": query, "chat_history": chat_history}) ``` ```python result['answer'] ``` ``` ' Ketanji Brown Jackson succeeded Justice Stephen Breyer on the United States Supreme Court.' ``` ## Using a different model for condensing the question This chain has two steps. First, it condenses the current question and the chat history into a standalone question. This is necessary to create a standanlone vector to use for retrieval. After that, it does retrieval and then answers the question using retrieval augmented generation with a separate model. Part of the power of the declarative nature of LangChain is that you can easily use a separate language model for each call. This can be useful to use a cheaper and faster model for the simpler task of condensing the question, and then a more expensive model for answering the question. Here is an example of doing so. ```python from langchain.chat_models import ChatOpenAI ``` ```python qa = ConversationalRetrievalChain.from_llm( ChatOpenAI(temperature=0, model="gpt-4"), vectorstore.as_retriever(), condense_question_llm = ChatOpenAI(temperature=0, model='gpt-3.5-turbo'), ) ``` ```python chat_history = [] query = "What did the president say about Ketanji Brown Jackson" result = qa({"question": query, "chat_history": chat_history}) ``` ```python chat_history = [(query, result["answer"])] query = "Did he mention who she succeeded" result = qa({"question": query, "chat_history": chat_history}) ``` ## Return Source Documents You can also easily return source documents from the ConversationalRetrievalChain. This is useful for when you want to inspect what documents were returned. ```python qa = ConversationalRetrievalChain.from_llm(OpenAI(temperature=0), vectorstore.as_retriever(), return_source_documents=True) ``` ```python chat_history = [] query = "What did the president say about Ketanji Brown Jackson" result = qa({"question": query, "chat_history": chat_history}) ``` ```python result['source_documents'][0] ``` ``` Document(page_content='Tonight. I call on the Senate to: Pass the Freedom to Vote Act. Pass the John Lewis Voting Rights Act. And while you’re at it, pass the Disclose Act so Americans can know who is funding our elections. \n\nTonight, I’d like to honor someone who has dedicated his life to serve this country: Justice Stephen Breyer—an Army veteran, Constitutional scholar, and retiring Justice of the United States Supreme Court. Justice Breyer, thank you for your service. \n\nOne of the most serious constitutional responsibilities a President has is nominating someone to serve on the United States Supreme Court. \n\nAnd I did that 4 days ago, when I nominated Circuit Court of Appeals Judge Ketanji Brown Jackson. One of our nation’s top legal minds, who will continue Justice Breyer’s legacy of excellence.', metadata={'source': '../../state_of_the_union.txt'}) ``` ## ConversationalRetrievalChain with `search_distance` If you are using a vector store that supports filtering by search distance, you can add a threshold value parameter. ```python vectordbkwargs = {"search_distance": 0.9} ``` ```python qa = ConversationalRetrievalChain.from_llm(OpenAI(temperature=0), vectorstore.as_retriever(), return_source_documents=True) chat_history = [] query = "What did the president say about Ketanji Brown Jackson" result = qa({"question": query, "chat_history": chat_history, "vectordbkwargs": vectordbkwargs}) ``` ## ConversationalRetrievalChain with `map_reduce` We can also use different types of combine document chains with the ConversationalRetrievalChain chain. ```python from langchain.chains import LLMChain from langchain.chains.question_answering import load_qa_chain from langchain.chains.conversational_retrieval.prompts import CONDENSE_QUESTION_PROMPT ``` ```python llm = OpenAI(temperature=0) question_generator = LLMChain(llm=llm, prompt=CONDENSE_QUESTION_PROMPT) doc_chain = load_qa_chain(llm, chain_type="map_reduce") chain = ConversationalRetrievalChain( retriever=vectorstore.as_retriever(), question_generator=question_generator, combine_docs_chain=doc_chain, ) ``` ```python chat_history = [] query = "What did the president say about Ketanji Brown Jackson" result = chain({"question": query, "chat_history": chat_history}) ``` ```python result['answer'] ``` ``` " The president said that Ketanji Brown Jackson is one of the nation's top legal minds, a former top litigator in private practice, a former federal public defender, from a family of public school educators and police officers, a consensus builder, and has received a broad range of support from the Fraternal Order of Police to former judges appointed by Democrats and Republicans." ``` ## ConversationalRetrievalChain with Question Answering with sources You can also use this chain with the question answering with sources chain. ```python from langchain.chains.qa_with_sources import load_qa_with_sources_chain ``` ```python llm = OpenAI(temperature=0) question_generator = LLMChain(llm=llm, prompt=CONDENSE_QUESTION_PROMPT) doc_chain = load_qa_with_sources_chain(llm, chain_type="map_reduce") chain = ConversationalRetrievalChain( retriever=vectorstore.as_retriever(), question_generator=question_generator, combine_docs_chain=doc_chain, ) ``` ```python chat_history = [] query = "What did the president say about Ketanji Brown Jackson" result = chain({"question": query, "chat_history": chat_history}) ``` ```python result['answer'] ``` ``` " The president said that Ketanji Brown Jackson is one of the nation's top legal minds, a former top litigator in private practice, a former federal public defender, from a family of public school educators and police officers, a consensus builder, and has received a broad range of support from the Fraternal Order of Police to former judges appointed by Democrats and Republicans. \nSOURCES: ../../state_of_the_union.txt" ``` ## ConversationalRetrievalChain with streaming to `stdout` Output from the chain will be streamed to `stdout` token by token in this example. ```python from langchain.chains.llm import LLMChain from langchain.callbacks.streaming_stdout import StreamingStdOutCallbackHandler from langchain.chains.conversational_retrieval.prompts import CONDENSE_QUESTION_PROMPT, QA_PROMPT from langchain.chains.question_answering import load_qa_chain # Construct a ConversationalRetrievalChain with a streaming llm for combine docs # and a separate, non-streaming llm for question generation llm = OpenAI(temperature=0) streaming_llm = OpenAI(streaming=True, callbacks=[StreamingStdOutCallbackHandler()], temperature=0) question_generator = LLMChain(llm=llm, prompt=CONDENSE_QUESTION_PROMPT) doc_chain = load_qa_chain(streaming_llm, chain_type="stuff", prompt=QA_PROMPT) qa = ConversationalRetrievalChain( retriever=vectorstore.as_retriever(), combine_docs_chain=doc_chain, question_generator=question_generator) ``` ```python chat_history = [] query = "What did the president say about Ketanji Brown Jackson" result = qa({"question": query, "chat_history": chat_history}) ``` ``` The president said that Ketanji Brown Jackson is one of the nation's top legal minds, a former top litigator in private practice, a former federal public defender, and from a family of public school educators and police officers. He also said that she is a consensus builder and has received a broad range of support from the Fraternal Order of Police to former judges appointed by Democrats and Republicans. ``` ```python chat_history = [(query, result["answer"])] query = "Did he mention who she succeeded" result = qa({"question": query, "chat_history": chat_history}) ``` ``` Ketanji Brown Jackson succeeded Justice Stephen Breyer on the United States Supreme Court. ``` ## get_chat_history Function You can also specify a `get_chat_history` function, which can be used to format the chat_history string. ```python def get_chat_history(inputs) -> str: res = [] for human, ai in inputs: res.append(f"Human:{human}\nAI:{ai}") return "\n".join(res) qa = ConversationalRetrievalChain.from_llm(OpenAI(temperature=0), vectorstore.as_retriever(), get_chat_history=get_chat_history) ``` ```python chat_history = [] query = "What did the president say about Ketanji Brown Jackson" result = qa({"question": query, "chat_history": chat_history}) ``` ```python result['answer'] ``` ``` " The president said that Ketanji Brown Jackson is one of the nation's top legal minds, a former top litigator in private practice, a former federal public defender, and from a family of public school educators and police officers. He also said that she is a consensus builder and has received a broad range of support from the Fraternal Order of Police to former judges appointed by Democrats and Republicans." ```