Exploring LangChain: A Practical Approach to Language Models and Retrieval-Augmented Generation (RAG)

LangChain is a powerful framework for building applications that incorporate large language models (LLMs).

- Wei-Meng Lee

It simplifies the process of embedding LLMs into complex workflows, enabling the creation of conversational agents, knowledge retrieval systems, automated pipelines, and other Al-driven applications. At its core, LangChain follows a modular design that allows developers to build “chains,” or sequences of actions, with customizable components like prompt templates, model settings, response parsing, and memory management. It also supports integration with external data sources such as document databases, search indices, APIs, and more— a feature commonly referred to as Retrieval-Augmented Generation (RAG). This flexibility empowers developers to create tailored solutions for diverse tasks, from customer support bots to data analysis tools that extract insights from extensive datasets.

With a growing suite of tools and agents, LangChain is a top choice for developers aiming to leverage LLMs for dynamic, data-driven, and interactive applications. It offers extensive customization options and is actively maintained to support the latest advancements in LLMs and AI.

In this article, I’ll guide you through the basics of using LangChain and its components. You'll learn how to combine different modules to create functional applications, including a RAG application for querying private documents using LLMs.

A Basic LangChain Example The easiest way to get started with LangChain is to begin with a simple example. First, let’s install the following libraries using the pip command:

For this example, you’ll be using LLMs from OpenAI, so you need to apply for an OpenAI API key and then save the API key in an environment variable:

Do remember that OpenAI operates with a pay-for-use model, where costs are typically based on usage, like the number of tokens processed in language model queries. Go to https://platform.openai.​com/docs/overview to sign up for an OpenAI account.