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| # Introduction | |
| **LangChain** is a framework for developing applications powered by large language models (LLMs). | |
| LangChain simplifies every stage of the LLM application lifecycle: | |
| - **Development**: Build your applications using LangChain's open-source [building blocks](/docs/concepts#langchain-expression-language-lcel), [components](/docs/concepts), and [third-party integrations](/docs/integrations/platforms/). | |
| Use [LangGraph](/docs/concepts/#langgraph) to build stateful agents with first-class streaming and human-in-the-loop support. | |
| - **Productionization**: Use [LangSmith](https://docs.smith.langchain.com/) to inspect, monitor and evaluate your chains, so that you can continuously optimize and deploy with confidence. | |
| - **Deployment**: Turn your LangGraph applications into production-ready APIs and Assistants with [LangGraph Cloud](https://langchain-ai.github.io/langgraph/cloud/). | |
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| Concretely, the framework consists of the following open-source libraries: | |
| - **`langchain-core`**: Base abstractions and LangChain Expression Language. | |
| - **`langchain-community`**: Third party integrations. | |
| - Partner packages (e.g. **`langchain-openai`**, **`langchain-anthropic`**, etc.): Some integrations have been further split into their own lightweight packages that only depend on **`langchain-core`**. | |
| - **`langchain`**: Chains, agents, and retrieval strategies that make up an application's cognitive architecture. | |
| - **[LangGraph](https://langchain-ai.github.io/langgraph)**: Build robust and stateful multi-actor applications with LLMs by modeling steps as edges and nodes in a graph. Integrates smoothly with LangChain, but can be used without it. | |
| - **[LangServe](/docs/langserve)**: Deploy LangChain chains as REST APIs. | |
| - **[LangSmith](https://docs.smith.langchain.com)**: A developer platform that lets you debug, test, evaluate, and monitor LLM applications. | |
| :::note | |
| These docs focus on the Python LangChain library. [Head here](https://js.langchain.com) for docs on the JavaScript LangChain library. | |
| ::: | |
| ## [Tutorials](/docs/tutorials) | |
| If you're looking to build something specific or are more of a hands-on learner, check out our [tutorials section](/docs/tutorials). | |
| This is the best place to get started. | |
| These are the best ones to get started with: | |
| - [Build a Simple LLM Application](/docs/tutorials/llm_chain) | |
| - [Build a Chatbot](/docs/tutorials/chatbot) | |
| - [Build an Agent](/docs/tutorials/agents) | |
| - [Introduction to LangGraph](https://langchain-ai.github.io/langgraph/tutorials/introduction/) | |
| Explore the full list of LangChain tutorials [here](/docs/tutorials), and check out other [LangGraph tutorials here](https://langchain-ai.github.io/langgraph/tutorials/). | |
| ## [How-to guides](/docs/how_to) | |
| [Here](/docs/how_to) you’ll find short answers to “How do I….?” types of questions. | |
| These how-to guides don’t cover topics in depth – you’ll find that material in the [Tutorials](/docs/tutorials) and the [API Reference](https://python.langchain.com/v0.2/api_reference/). | |
| However, these guides will help you quickly accomplish common tasks. | |
| Check out [LangGraph-specific how-tos here](https://langchain-ai.github.io/langgraph/how-tos/). | |
| ## [Conceptual guide](/docs/concepts) | |
| Introductions to all the key parts of LangChain you’ll need to know! [Here](/docs/concepts) you'll find high level explanations of all LangChain concepts. | |
| For a deeper dive into LangGraph concepts, check out [this page](https://langchain-ai.github.io/langgraph/concepts/). | |
| ## [API reference](https://python.langchain.com/v0.2/api_reference/) | |
| Head to the reference section for full documentation of all classes and methods in the LangChain Python packages. | |
| ## Ecosystem | |
| ### [🦜🛠️ LangSmith](https://docs.smith.langchain.com) | |
| Trace and evaluate your language model applications and intelligent agents to help you move from prototype to production. | |
| ### [🦜🕸️ LangGraph](https://langchain-ai.github.io/langgraph) | |
| Build stateful, multi-actor applications with LLMs. Integrates smoothly with LangChain, but can be used without it. | |
| ## Additional resources | |
| ### [Versions](/docs/versions/overview/) | |
| See what changed in v0.2, learn how to migrate legacy code, and read up on our release/versioning policies, and more. | |
| ### [Security](/docs/security) | |
| Read up on [security](/docs/security) best practices to make sure you're developing safely with LangChain. | |
| ### [Integrations](/docs/integrations/providers/) | |
| LangChain is part of a rich ecosystem of tools that integrate with our framework and build on top of it. Check out our growing list of [integrations](/docs/integrations/providers/). | |
| ### [Contributing](/docs/contributing) | |
| Check out the developer's guide for guidelines on contributing and help getting your dev environment set up. | |