# LangChain

LangChain is a software framework that helps facilitate the integration of large language models (LLMs) into applications. As a language model integration framework, LangChain's use-cases largely overlap with those of language models in general, including document analysis and summarization, chatbots, and code analysis.

## History

LangChain was launched in October 2022 as an open source project by Harrison Chase, while working at machine learning startup Robust Intelligence. The project quickly garnered popularity, with improvements from hundreds of contributors on GitHub, trending discussions on Twitter, lively activity on the project's Discord server, many YouTube tutorials, and meetups in San Francisco and London. In April 2023, LangChain had incorporated and the new startup raised over $20 million in funding at a valuation of at least $200 million from venture firm Sequoia Capital, a week after announcing a $10 million seed investment from Benchmark.
In the third quarter of 2023, the LangChain Expression Language (LCEL) was introduced, which provides a declarative way to define chains of actions.
In October 2023 LangChain introduced LangServe, a deployment tool to host LCEL code as a production-ready API.

## Capabilities

LangChain's developers highlight the framework's applicability to use-cases including chatbots, retrieval-augmented generation, document summarization, and synthetic data generation.
As of March 2023, LangChain included integrations with systems including Amazon, Google, and Microsoft Azure cloud storage; API wrappers for news, movie information, and weather; Bash for summarization, syntax and semantics checking, and execution of shell scripts; multiple web scraping subsystems and templates; few-shot learning prompt generation support; finding and summarizing "todo" tasks in code; Google Drive documents, spreadsheets, and presentations summarization, extraction, and creation; Google Search and Microsoft Bing web search; OpenAI, Anthropic, and Hugging Face language models; iFixit repair guides and wikis search and summarization; MapReduce for question answering, combining documents, and question generation; N-gram overlap scoring; PyPDF, pdfminer, fitz, and pymupdf for PDF file text extraction and manipulation; Python and JavaScript code generation, analysis, and debugging; Milvus vector database to store and retrieve vector embeddings; Weaviate vector database to cache embedding and data objects; Redis cache database storage; Python RequestsWrapper and other methods for API requests; SQL and NoSQL databases including JSON support; Streamlit, including for logging; text mapping for k-nearest neighbors search; time zone conversion and calendar operations; tracing and recording stack symbols in threaded and asynchronous subprocess runs; and the Wolfram Alpha website and SDK. As of April 2023, it can read from more than 50 document types and data sources.

## LangChain tools

| Tool name | Account required? | API key required? | Licencing | Features | Documentation URL |
| Alpha Vantage | No | Yes | Proprietary | Financial data, analytics | https://python.langchain.com/docs/integrations/tools/alpha_vantage |
| Apify | No | Yes | Commercial | Web scraping, automation | https://python.langchain.com/docs/integrations/providers/apify/ |
| ArXiv | No | No | Open Source | Scientific papers, research | https://python.langchain.com/docs/integrations/tools/arxiv |
| AWS Lambda | Yes | Yes | Proprietary | Serverless computing | https://python.langchain.com/docs/integrations/tools/awslambda |
| Bash | No | No | Open source | Shell environment access | https://python.langchain.com/docs/integrations/tools/bash |
| Bearly Code Interpreter | No | Yes | Commercial | Remote Python code execution | https://python.langchain.com/docs/integrations/tools/bearly |
| Bing Search | No | Yes | Proprietary | Search engine | https://python.langchain.com/docs/integrations/tools/bing_search |
| Brave Search | No | No | Open source | Privacy-focused search | https://python.langchain.com/docs/integrations/tools/brave_search |
| ChatGPT Plugins | No | Yes | Proprietary | ChatGPT | https://python.langchain.com/docs/integrations/tools/chatgpt_plugins |
| Connery | No | Yes | Commercial | API actions | https://python.langchain.com/docs/integrations/tools/connery |
| Dall-E Image Generator | No | Yes | Proprietary | Text-to-image generation | https://python.langchain.com/docs/integrations/tools/dalle_image_generator |
| DataForSEO | No | Yes | Commercial | SEO data, analytics | https://python.langchain.com/docs/integrations/tools/dataforseo |
| DuckDuckGo Search | No | No | Open source | Privacy-focused search | https://python.langchain.com/docs/integrations/tools/ddg |
| E2B Data Analysis | No | No | Open source | Data analysis | https://python.langchain.com/docs/integrations/tools/e2b_data_analysis |
| Eden AI | No | Yes | Commercial | AI tools, APIs | https://python.langchain.com/docs/integrations/tools/edenai_tools |
| Eleven Labs Text2Speech | No | Yes | Commercial | Text-to-speech | https://python.langchain.com/docs/integrations/tools/eleven_labs_tts |
| Exa Search | No | Yes | Commercial | Web search | https://python.langchain.com/docs/integrations/tools/exa_search |
| File System | No | No | Open source | File system interaction | https://python.langchain.com/docs/integrations/tools/filesystem |
| Golden Query | No | Yes | Commercial | Natural language queries | https://python.langchain.com/docs/integrations/tools/golden_query |
| Google Cloud Text-to-Speech | Yes | Yes | Proprietary | Text-to-speech | https://python.langchain.com/docs/integrations/tools/google_cloud_texttospeech |
| Google Drive | Yes | Yes | Proprietary | Google Drive access | https://python.langchain.com/docs/integrations/tools/google_drive |
| Google Finance | Yes | Yes | Proprietary | Financial data | https://python.langchain.com/docs/integrations/tools/google_finance |
| Google Jobs | Yes | Yes | Proprietary | Job search | https://python.langchain.com/docs/integrations/tools/google_jobs |
| Google Lens | Yes | Yes | Proprietary | Visual search, recognition | https://python.langchain.com/docs/integrations/tools/google_lens |
| Google Places | Yes | Yes | Proprietary | Location-based services | https://python.langchain.com/docs/integrations/tools/google_places |
| Google Scholar | Yes | Yes | Proprietary | Scholarly article search | https://python.langchain.com/docs/integrations/tools/google_scholar |
| Google Search | Yes | Yes | Proprietary | Search engine | https://python.langchain.com/docs/integrations/tools/google_search |
| Google Serper | No | Yes | Commercial | SERP scraping | https://python.langchain.com/docs/integrations/tools/google_serper |
| Google Trends | Yes | Yes | Proprietary | Trend data | https://python.langchain.com/docs/integrations/tools/google_trends |
| Gradio | No | No | Open source | Machine learning UIs | https://python.langchain.com/docs/integrations/tools/gradio_tools |
| GraphQL | No | No | Open source | API queries | https://python.langchain.com/docs/integrations/tools/graphql |
| HuggingFace Hub | No | No | Open source | Hugging Face models, datasets | https://python.langchain.com/docs/integrations/tools/huggingface_tools |
| Human as a tool | No | No | N/A | Human input | https://python.langchain.com/docs/integrations/tools/human_tools |
| IFTTT WebHooks | No | Yes | Commercial | Web service automation | https://python.langchain.com/docs/integrations/tools/ifttt |
| Ionic Shopping | No | Yes | Commercial | Shopping | https://python.langchain.com/docs/integrations/tools/ionic_shopping |
| Lemon Agent | No | Yes | Commercial | Lemon AI interaction | https://python.langchain.com/docs/integrations/tools/lemonai |
| Memorize | No | No | Open source | Fine-tune LLM to memorize information using unsupervised learning | https://python.langchain.com/docs/integrations/tools/memorize |
| Nuclia | No | Yes | Commercial | Indexing of unstructured data | https://python.langchain.com/docs/integrations/tools/nuclia |
| OpenWeatherMap | No | Yes | Commercial | Weather data | https://python.langchain.com/docs/integrations/tools/openweathermap |
| Polygon Stock Market API | No | Yes | Commercial | Stock market data | https://python.langchain.com/docs/integrations/tools/polygon |
| PubMed | No | No | Open source | Biomedical literature | https://python.langchain.com/docs/integrations/tools/pubmed |
| Python REPL | No | No | Open source | Python shell | https://python.langchain.com/docs/integrations/tools/python |
| Reddit Search | No | No | Open source | Reddit search | https://python.langchain.com/docs/integrations/tools/reddit_search |
| Requests | No | No | Open source | HTTP requests | https://python.langchain.com/docs/integrations/tools/requests |
| SceneXplain | No | No | Open source | Model explanations | https://python.langchain.com/docs/integrations/tools/sceneXplain |
| Search | No | No | Open source | Query various search services | https://python.langchain.com/docs/integrations/tools/search_tools |
| SearchApi | No | Yes | Commercial | Query various search services | https://python.langchain.com/docs/integrations/tools/searchapi |
| SearxNG | No | No | Open source | Privacy-focused search | https://python.langchain.com/docs/integrations/tools/searx_search |
| Semantic Scholar API | No | No | Open source | Academic paper search | https://python.langchain.com/docs/integrations/tools/semanticscholar |
| SerpAPI | No | Yes | Commercial | Search engine results page scraping | https://python.langchain.com/docs/integrations/tools/serpapi |
| StackExchange | No | No | Open source | Stack Exchange access | https://python.langchain.com/docs/integrations/tools/stackexchange |
| Tavily Search | No | Yes | Commercial | Question answering | https://python.langchain.com/docs/integrations/tools/tavily_search |
| Twilio | No | Yes | Commercial | Communication APIs | https://python.langchain.com/docs/integrations/tools/twilio |
| Wikidata | No | No | Open source | Structured data access | https://python.langchain.com/docs/integrations/tools/wikidata |
| Wikipedia | No | No | Open source | Wikipedia access | https://python.langchain.com/docs/integrations/tools/wikipedia |
| Wolfram Alpha | No | Yes | Proprietary | Computational knowledge | https://python.langchain.com/docs/integrations/tools/wolfram_alpha |
| Yahoo Finance News | No | Yes | Commercial | Financial news | https://python.langchain.com/docs/integrations/tools/yahoo_finance_news |
| Youtube | No | Yes | Commercial | YouTube access | https://python.langchain.com/docs/integrations/tools/youtube |
| Zapier Natural Language Actions | No | Yes | Commercial | Workflow automation | https://python.langchain.com/docs/integrations/tools/zapier |