langchain/docs/modules/indexes/chain_examples/vector_db_qa_with_sources.ipynb

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  {
   "cell_type": "markdown",
   "id": "efc5be67",
   "metadata": {},
   "source": [
    "# Retrieval Question Answering with Sources\n",
    "\n",
    "This notebook goes over how to do question-answering with sources over an Index. It does this by using the `RetrievalQAWithSourcesChain`, which does the lookup of the documents from an Index. "
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "id": "1c613960",
   "metadata": {},
   "outputs": [],
   "source": [
    "from langchain.embeddings.openai import OpenAIEmbeddings\n",
    "from langchain.embeddings.cohere import CohereEmbeddings\n",
    "from langchain.text_splitter import CharacterTextSplitter\n",
    "from langchain.vectorstores.elastic_vector_search import ElasticVectorSearch\n",
    "from langchain.vectorstores import Chroma"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "id": "17d1306e",
   "metadata": {},
   "outputs": [],
   "source": [
    "with open('../../state_of_the_union.txt') as f:\n",
    "    state_of_the_union = f.read()\n",
    "text_splitter = CharacterTextSplitter(chunk_size=1000, chunk_overlap=0)\n",
    "texts = text_splitter.split_text(state_of_the_union)\n",
    "\n",
    "embeddings = OpenAIEmbeddings()"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "id": "0e745d99",
   "metadata": {},
   "outputs": [
    {
     "name": "stdout",
     "output_type": "stream",
     "text": [
      "Running Chroma using direct local API.\n",
      "Using DuckDB in-memory for database. Data will be transient.\n"
     ]
    }
   ],
   "source": [
    "docsearch = Chroma.from_texts(texts, embeddings, metadatas=[{\"source\": f\"{i}-pl\"} for i in range(len(texts))])"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "id": "8aa571ae",
   "metadata": {},
   "outputs": [],
   "source": [
    "from langchain.chains import RetrievalQAWithSourcesChain"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "id": "aa859d4c",
   "metadata": {},
   "outputs": [],
   "source": [
    "from langchain import OpenAI\n",
    "\n",
    "chain = RetrievalQAWithSourcesChain.from_chain_type(OpenAI(temperature=0), chain_type=\"stuff\", retriever=docsearch.as_retriever())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 6,
   "id": "8ba36fa7",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'answer': ' The president honored Justice Breyer for his service and mentioned his legacy of excellence.\\n',\n",
       " 'sources': '31-pl'}"
      ]
     },
     "execution_count": 6,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "chain({\"question\": \"What did the president say about Justice Breyer\"}, return_only_outputs=True)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "718ecbda",
   "metadata": {},
   "source": [
    "## Chain Type\n",
    "You can easily specify different chain types to load and use in the RetrievalQAWithSourcesChain chain. For a more detailed walkthrough of these types, please see [this notebook](qa_with_sources.ipynb).\n",
    "\n",
    "There are two ways to load different chain types. First, you can specify the chain type argument in the `from_chain_type` method. This allows you to pass in the name of the chain type you want to use. For example, in the below we change the chain type to `map_reduce`."
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 7,
   "id": "8b35b30a",
   "metadata": {},
   "outputs": [],
   "source": [
    "chain = RetrievalQAWithSourcesChain.from_chain_type(OpenAI(temperature=0), chain_type=\"map_reduce\", retriever=docsearch.as_retriever())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "58bd424f",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'answer': ' The president said \"Justice Breyer—an Army veteran, Constitutional scholar, and retiring Justice of the United States Supreme Court. Justice Breyer, thank you for your service.\"\\n',\n",
       " 'sources': '31-pl'}"
      ]
     },
     "execution_count": 8,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "chain({\"question\": \"What did the president say about Justice Breyer\"}, return_only_outputs=True)"
   ]
  },
  {
   "cell_type": "markdown",
   "id": "21e14eed",
   "metadata": {},
   "source": [
    "The above way allows you to really simply change the chain_type, but it does provide a ton of flexibility over parameters to that chain type. If you want to control those parameters, you can load the chain directly (as you did in [this notebook](qa_with_sources.ipynb)) and then pass that directly to the the RetrievalQAWithSourcesChain chain with the `combine_documents_chain` parameter. For example:"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 10,
   "id": "af35f0c6",
   "metadata": {},
   "outputs": [],
   "source": [
    "from langchain.chains.qa_with_sources import load_qa_with_sources_chain\n",
    "qa_chain = load_qa_with_sources_chain(OpenAI(temperature=0), chain_type=\"stuff\")\n",
    "qa = RetrievalQAWithSourcesChain(combine_documents_chain=qa_chain, retriever=docsearch.as_retriever())"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 11,
   "id": "c91fdc8a",
   "metadata": {},
   "outputs": [
    {
     "data": {
      "text/plain": [
       "{'answer': ' The president honored Justice Breyer for his service and mentioned his legacy of excellence.\\n',\n",
       " 'sources': '31-pl'}"
      ]
     },
     "execution_count": 11,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "qa({\"question\": \"What did the president say about Justice Breyer\"}, return_only_outputs=True)"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "id": "3c594296",
   "metadata": {},
   "outputs": [],
   "source": []
  }
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