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How-to guides

Here you'll find answers to "How do I...?" types of questions. These guides are goal-oriented and concrete; they're meant to help you complete a specific task. For conceptual explanations see the Conceptual guide. For end-to-end walkthroughs see Tutorials. For comprehensive descriptions of every class and function see the API Reference.

Installation​

Key features​

This highlights functionality that is core to using LangChain.

LangChain Expression Language is a way to create arbitrary custom chains. It is built on the Runnable protocol.

LCEL cheatsheet: For a quick overview of how to use the main LCEL primitives.

Components​

These are the core building blocks you can use when building applications.

Prompt templates​

Prompt Templates are responsible for formatting user input into a format that can be passed to a language model.

Chat models​

Chat Models are newer forms of language models that take messages in and output a message.

LLMs​

What LangChain calls LLMs are older forms of language models that take a string in and output a string.

Document loaders​

Document Loaders are responsible for loading documents from a variety of sources.

Text splitters​

Text Splitters take a document and split into chunks that can be used for retrieval.

Vector stores​

Vector stores are databases that can efficiently store and retrieve embeddings.

Retrievers​

Retrievers are responsible for taking a query and returning relevant documents.

Agents​

Function Tool calling​

Tools​

Embedding Models​

Output Parsers​