angChain.js. Hit the ground running using Templates for reference. 
  * **Productionize** : Use LangSmith to inspect, test and monitor your chains, so that you can constantly improve and deploy with confidence. 
  * **Deploy** : Turn any chain into an API with LangServe. 

##  LangChain Libraries  ​

The main value props of the LangChain packages are:

  1. **Components** : composable tools and integrations for working with language models. Components are modular and easy-to-use, whether you are using the rest of the LangChain framework or not 
  2. **Off-the-shelf chains** : built-in assemblages of components for accomplishing higher-level tasks 

Off-the-shelf chains make it easy to get started. Components make it easy to
customize existing chains and build new ones.

The LangChain libraries themselves are made up of several different packages.

  * **` langchain-core ` ** : Base abstractions and LangChain Expression Language. 
  * **` langchain-community ` ** : Third party integrations. 
  * **` langchain ` ** : Chains, agents, and retrieval strategies that make up an application's cognitive architecture. 

##  Get started  ​

[ Here’s ](/docs/get_started/installation) how to install LangChain, set up
your environment, and start building.

We recommend following our [ Quickstart ](/docs/get_started/quickstart) guide
to familiarize yourself with the framework by building your first LangChain
application.

Read up on our [ Security ](/docs/security) best practices to make sure you're
developing safely with LangChain.

note

These docs focus on the Python LangChain library. [ Head here
](https://js.langchain.com) for docs on the JavaScript LangChain library.

##  LangChain Expression Language (LCEL)  ​

LCEL is a declarative way to compose chains. LCEL was designed from day 1 to
support putting prototypes in production, with no code changes, from the
simplest “prompt + LLM” chain to the most complex chains.

  * **[ Overview ](/docs/expression_language/) ** : LCEL and its benefits 
  * **[ Interface ](/docs/expression_language/interface) ** : The standard interface for LCEL objects 
  * **[ How-to ](/docs/expression_language/how_to) ** : Key features of LCEL 
  * **[ Cookbook ](/docs/expression_language/cookbook) ** : Example code for accomplishing common tasks 

##  Modules  ​

LangChain provides standard, extendable interfaces and integrations for the
following modules:

####  [ Model I/O ](/docs/modules/model_io/) ​

Interface with language models

####  [ Retrieval ](/docs/modules/data_connection/) ​

Interface with application-specific data

####  [ Agents ](/docs/modules/agents/) ​

Let models choose which tools to use given high-level directives

##  Examples, ecosystem, and resources  ​

###  [ Use cases ](/docs/use_cases/question_answering/) ​

Walkthroughs and techniques for common end-to-end use cases, like:

  * [ Document question answering ](/docs/use_cases/question_answering/)
  * [ Chatbots ](/docs/use_cases/chatbots/)
  * [ Analyzing structured data ](/docs/use_cases/sql/)
  * and much more... 

###  [ 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/) .

###  [ Guides ](/docs/guides/debugging) ​

Best practices for developing with LangChain.

###  [ API reference ](https://api.python.langchain.com) ​

Head to the reference section for full documentation of all classes and
methods in the LangChain and LangChain Experimental Python packages.

###  [ Developer's guide ](/docs/contributing) ​

Check out the developer's guide for guidelines on contributing and help
getting your dev environment set up.

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