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LangChain: Building LLM Applications with Python

From basics to production-ready AI agents and RAG systems

📖 Total Reading Time: 90-120 minutes 📊 Difficulty: Beginner-Intermediate 💻 Code Examples: 25 📝 Exercises: 8

Series Overview

This series provides a comprehensive introduction to LangChain, the most widely adopted framework for building applications powered by Large Language Models (LLMs). With over 80,000 GitHub stars and adoption by companies like Uber, LinkedIn, and Klarna, LangChain has become the de facto standard for LLM application development.

Updated for LangChain v1.0 (released October 2025), this series covers the latest features including the new create_agent API, LangChain Expression Language (LCEL), and integration with the broader ecosystem including LangGraph for complex workflows and LangSmith for observability.

graph TB subgraph LangChain["LangChain Ecosystem"] LC[LangChain
Core Framework] LG[LangGraph
Agent Orchestration] LS[LangSmith
Observability] end subgraph Models["LLM Providers"] M1[OpenAI] M2[Anthropic] M3[Google] end subgraph Apps["Applications"] A1[Chatbots] A2[RAG Systems] A3[AI Agents] end Models --> LC LC --> Apps LC --> LG LC --> LS style LC fill:#667eea,color:#fff style LG fill:#11998e,color:#fff style LS fill:#f093fb,color:#fff

Why Learn LangChain?

The Challenge: Building LLM applications from scratch requires handling complex tasks like prompt management, model switching, memory management, tool integration, and error handling. Without a framework, developers spend more time on infrastructure than on actual application logic.

The Solution: LangChain provides a unified interface for working with any LLM provider, composable components for building complex workflows, and production-ready features like streaming, caching, and observability. With just a few lines of code, you can build sophisticated AI applications that were previously impossible.

Content of All 5 Chapters

Chapter 1: What is LangChain?
📖 15-20 minutes 💻 4 examples 📝 2 exercises 📊 Beginner
Understand the challenges of LLM application development and how LangChain addresses them. Learn about the LangChain ecosystem (LangChain, LangGraph, LangSmith) and the major changes in v1.0.
Chapter 2: Core Components
📖 20-25 minutes 💻 5 examples 📝 2 exercises 📊 Beginner
Master the fundamental building blocks: Chat Models, Prompt Templates, Output Parsers, and LangChain Expression Language (LCEL). Build your first chain from scratch.
Chapter 3: Agents and Tools
📖 20-25 minutes 💻 6 examples 📝 2 exercises 📊 Beginner-Intermediate
Learn to build AI agents using the new create_agent API (v1.0). Define custom tools, integrate built-in capabilities like web search, and orchestrate agent execution.
Chapter 4: RAG (Retrieval-Augmented Generation)
📖 20-25 minutes 💻 6 examples 📝 1 exercise 📊 Intermediate
Build knowledge-grounded AI systems with RAG. Cover document loading, text splitting, embeddings, vector stores, and retrieval chains with production best practices.
Chapter 5: Production Deployment
📖 15-20 minutes 💻 4 examples 📝 1 exercise 📊 Intermediate
Take your applications to production with LangSmith observability, LangGraph for complex workflows, MCP integration, and performance optimization best practices.

Target Audience

Prerequisite Knowledge

Required:

Recommended:

Key Tools

Learning Path

For Complete Beginners:
Chapter 1 → Chapter 2 → Chapter 3 → Chapter 4 → Chapter 5
Time required: 90-120 minutes

For Developers Familiar with LLM APIs:
Chapter 1 (skim) → Chapter 2 → Chapter 3 → Chapter 5
Time required: 60-80 minutes

Quick RAG Implementation:
Chapter 1 → Chapter 2 → Chapter 4
Time required: 50-60 minutes

Next Steps

After completing this series, we recommend:

Let's Get Started!

Ready to build powerful LLM applications? Start with Chapter 1 and learn how LangChain can transform your AI development workflow!

Read Chapter 1 →

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