LangChain and OpenRouter in Python

vinod — Thu, 27 Nov 2025 12:03:44 +0000

🚀 create_agent Using LangChain and OpenRouter in Python

Artificial Intelligence doesn’t have to be complicated. In this short tutorial, I’ll show you how to build a simple create_agent using Python, LangChain, and OpenRouter in just a few steps. This is perfect for beginners who want to understand how AI APIs work in real projects.

👉 GitHub Repository: https://github.com/vinodnextcoder/langchain-tutorials

🧠 What We’re Building

We’ll create a small Python script that:

Connects to an AI model using OpenRouter
Uses LangChain to manage the conversation
Asks a simple question
Prints the AI’s response in the terminal

Example question:

“What is artificial intelligence in simple terms?”

📁 Project Structure

langchain_python/
└── python_example/
    ├── createagent.py
    ├── .env
    └── README.md

✅ Prerequisites

Before starting, make sure you have:

Python 3.9+
An OpenRouter API key
Basic knowledge of running Python scripts

📦 Step 1: Install Required Packages

Go to the python_example folder and run:

pip install langchain langchain-openai python-dotenv

🔐 Step 2: Add Your API Key Safely

Create a file named .env inside python_example and add:

OPENROUTER_API_KEY=your_api_key_here

This keeps your API key secure and out of your source code.

🧑‍💻 Step 3: The Python Script (`createagent.py`)

Your script does the following:

Loads the API key from .env
Connects to OpenRouter using an OpenAI-compatible setup
Creates a simple LangChain agent
Sends a user question
Prints the AI’s response safely

The key idea is simple:

You send a message → the AI processes it → you print the response.

🧑‍💻 Step 4: The Python code

import os
from langchain.agents import create_agent
from dotenv import load_dotenv
from langchain_openai import ChatOpenAI

# Load environment variables
load_dotenv()

# Get API key
OPENROUTER_KEY = os.getenv("OPENROUTER_API_KEY")
if not OPENROUTER_KEY:
    raise ValueError("Missing OPENROUTER_API_KEY in environment")

# Set OpenAI-compatible environment variables for OpenRouter
os.environ["OPENAI_API_KEY"] = OPENROUTER_KEY
os.environ["OPENAI_BASE_URL"] = "https://openrouter.ai/api/v1"

# Create LLM
llm = ChatOpenAI(
    model="mistralai/mistral-7b-instruct:free",
    temperature=0.7,
    api_key=OPENROUTER_KEY,
)

# Create agent
agent = create_agent(
    llm,
    tools=[],
    system_prompt="You are a helpful assistant. Answer in simple words."
)

# User input
user_question = "What is artificial intelligence in simple terms?"

# Invoke agent
response = agent.invoke({
    "messages": [
        {"role": "user", "content": user_question}
    ]
})

# Extract and print AI response safely
if "messages" in response and len(response["messages"]) > 0:
    ai_message = response["messages"][-1]
    print(ai_message.content)
else:
    print("No response received from the agent.")

▶️ Step 5: Run the Project

From the python_example folder, run:

python createagent.py

🧾 Sample Output

Artificial intelligence is when computers are taught to think and learn like humans to perform tasks such as answering questions and making decisions.

💡 What You Learn From This Project

With this small example, you learn:

How to use environment variables in Python
How to connect Python to an AI model
How LangChain agents work at a basic level
How to safely extract and print an AI response

✅ Final Thoughts

This project is a great starting point for anyone entering AI development with Python. With just a few steps, you’ve built a working AI-powered chatbot using modern tools like LangChain and OpenRouter.

If you’re learning AI integration, this is the perfect first milestone. ✅

DEV Community: vinod