LangChain-06 RAG With Source Doc 通过文档进行检索增强 原创

安装依赖

pip install --upgrade --quiet  langchain-core langchain-community langchain-openai

编辑代码

from operator import itemgetter
from langchain_core.messages import AIMessage, HumanMessage, get_buffer_string
from langchain_core.prompts import format_document
from langchain_core.runnables import RunnableParallel, RunnablePassthrough, RunnableLambda
from langchain_openai.chat_models import ChatOpenAI
from langchain_openai import OpenAIEmbeddings
from langchain.prompts.prompt import PromptTemplate
from langchain.prompts.chat import ChatPromptTemplate
from langchain_core.output_parsers import StrOutputParser
from langchain_community.vectorstores import DocArrayInMemorySearch
from langchain.memory import ConversationBufferMemory


vectorstore = DocArrayInMemorySearch.from_texts(
        ["wuzikang worked at earth", "sam worked at home", "harrison worked at kensho"], embedding=OpenAIEmbeddings()
    )
retriever = vectorstore.as_retriever()

_template = """Given the following conversation and a follow up question, rephrase the follow up question to be a standalone question, in its original language.

Chat History:
{chat_history}
Follow Up Input: {question}
Standalone question:"""
CONDENSE_QUESTION_PROMPT = PromptTemplate.from_template(_template)

template = """Answer the question based only on the following context:
{context}

Question: {question}
"""
ANSWER_PROMPT = ChatPromptTemplate.from_template(template)
DEFAULT_DOCUMENT_PROMPT = PromptTemplate.from_template(template="{page_content}")


def _combine_documents(
    docs, document_prompt=DEFAULT_DOCUMENT_PROMPT, document_separator="\n\n"
):
    doc_strings = [format_document(doc, document_prompt) for doc in docs]
    return document_separator.join(doc_strings)


_inputs = RunnableParallel(
    standalone_question=RunnablePassthrough.assign(
        chat_history=lambda x: get_buffer_string(x["chat_history"])
    )
    | CONDENSE_QUESTION_PROMPT
    | ChatOpenAI(temperature=0)
    | StrOutputParser(),
)


memory = ConversationBufferMemory(
    return_messages=True, output_key="answer", input_key="question"
)

# First we add a step to load memory
# This adds a "memory" key to the input object
loaded_memory = RunnablePassthrough.assign(
    chat_history=RunnableLambda(memory.load_memory_variables) | itemgetter("history"),
)
# Now we calculate the standalone question
standalone_question = {
    "standalone_question": {
        "question": lambda x: x["question"],
        "chat_history": lambda x: get_buffer_string(x["chat_history"]),
    }
    | CONDENSE_QUESTION_PROMPT
    | ChatOpenAI(temperature=0)
    | StrOutputParser(),
}
# Now we retrieve the documents
retrieved_documents = {
    "docs": itemgetter("standalone_question") | retriever,
    "question": lambda x: x["standalone_question"],
}
# Now we construct the inputs for the final prompt
final_inputs = {
    "context": lambda x: _combine_documents(x["docs"]),
    "question": itemgetter("question"),
}
# And finally, we do the part that returns the answers
answer = {
    "answer": final_inputs | ANSWER_PROMPT | ChatOpenAI(),
    "docs": itemgetter("docs"),
}
# And now we put it all together!
final_chain = loaded_memory | standalone_question | retrieved_documents | answer

inputs = {"question": "where did sam work?"}
result = final_chain.invoke(inputs)
print(f"result1: {result}")

# memory
memory.save_context(inputs, {"answer": result["answer"].content})
memory.load_memory_variables({})
inputs = {"question": "but where did he really work?"}
result2 = final_chain.invoke(inputs)
print(f"result2: {result2}")

运行代码

➜ python3 test06.py
/Users/wuzikang/Desktop/py/langchain_test/own_learn/env/lib/python3.12/site-packages/pydantic/_migration.py:283: UserWarning: `pydantic.error_wrappers:ValidationError` has been moved to `pydantic:ValidationError`.
  warnings.warn(f'`{import_path}` has been moved to `{new_location}`.')
result1: {'answer': AIMessage(content='Sam worked at home.', response_metadata={'finish_reason': 'stop', 'logprobs': None}), 'docs': [Document(page_content='sam worked at home'), Document(page_content='wuzikang worked at earth'), Document(page_content='harrison worked at kensho')]}
result2: {'answer': AIMessage(content='Sam actually worked at home.', response_metadata={'finish_reason': 'stop', 'logprobs': None}), 'docs': [Document(page_content='sam worked at home'), Document(page_content='wuzikang worked at earth'), Document(page_content='harrison worked at kensho')]}