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LangChain
The framework for building LLM apps — chains, agents, RAG, and 600+ integrations.
0Free
AI Agents RAG Frameworks
Overview
LangChain is the leading framework for building LLM-powered applications, providing composable components for chains, agents, RAG pipelines, and tool integrations.
Key Features
- LCEL (LangChain Expression Language) for composing chains
- LangGraph for stateful, multi-actor agent workflows
- 600+ integrations with LLMs, vector stores, tools
- RAG primitives: document loaders, splitters, retrievers
- Memory and conversation history management
- LangSmith for tracing, debugging, and evaluation
Real-World Workflows
Build a document Q&A bot with RAG
- 1Load documents using LangChain document loaders (PDF, web, S3)
- 2Split text with RecursiveCharacterTextSplitter
- 3Embed and store in a vector database like Chroma or Pinecone
- 4Create a RetrievalQA chain and expose it as an API
Build a ReAct agent with tools
- 1Define tools (web search, calculator, database query)
- 2Use create_react_agent with your tool list and LLM
- 3The agent iteratively reasons, calls tools, and observes results
- 4Trace execution in LangSmith to debug reasoning steps
Getting Started
pip install langchain langchain-openai from langchain_openai import ChatOpenAI from langchain_core.messages import HumanMessage model = ChatOpenAI(model='gpt-4o') response = model.invoke([HumanMessage(content='Hello!')]) print(response.content)
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