Installation & Setup

Get LangChain installed and your development environment ready in minutes.

Prerequisites

• Python 3.9 or later
• An API key from an LLM provider (OpenAI, Anthropic, etc.)
• Basic familiarity with Python and virtual environments

Install LangChain

pip install langchain langchain-openai

For the full ecosystem (community integrations, experimental features):

pip install langchain langchain-community langchain-openai langchain-chroma

Set Up Your API Key

Create a .env file in your project root:

OPENAI_API_KEY=sk-your-key-here

Load it in Python:

from dotenv import load_dotenv
load_dotenv()

Or export directly in your shell:

export OPENAI_API_KEY="sk-your-key-here"

Verify the Installation

from langchain_openai import ChatOpenAI
 
llm = ChatOpenAI(model="gpt-4o-mini")
response = llm.invoke("Say hello in one sentence.")
print(response.content)

If you see a response, you're all set!

Project Structure

A typical LangChain project looks like:

my-agent/
├── .env
├── requirements.txt
├── main.py
├── chains/
├── tools/
└── prompts/

Next Steps

Now that your environment is ready, let's build your first chain in the next topic.