How to Use the OpenRouter API to Access Multiple AI Models via Python

One of the quickest ways to call multiple AI models from a single Python script is to use OpenRouter’s API, which acts as a unified routing layer between your code and multiple AI providers. By the end of this guide, you’ll access models from several providers through one unified API, as shown in the image below:

This convenience matters because the AI ecosystem is highly fragmented: each provider exposes its own API, authentication scheme, rate limits, and model lineup. Working with multiple providers often requires additional setup and integration effort, especially when you want to experiment with different models, compare outputs, or evaluate trade-offs for a specific task.

OpenRouter gives you access to thousands of models from leading providers such as OpenAI, Anthropic, Mistral, Google, and Meta. You switch between them without changing your application code.

Prerequisites

Before diving into OpenRouter, you should be comfortable with Python fundamentals like importing modules, working with dictionaries, handling exceptions, and using environment variables. If you’re familiar with these basics, the first step is authenticating with OpenRouter’s API.

Step 1: Connect to OpenRouter’s API

Before using OpenRouter, you need to create an account and generate an API key. Some models require prepaid credits for access, but you can start with free access to test the API and confirm that everything is working.

To generate an API key:

• Create an account at OpenRouter.ai or sign in if you already have an account.
• Select Keys from the dropdown menu and create an API key.
• Fill in the name, something like OpenRouter Testing.
• Leave the remaining defaults and click Create.

Copy the generated key and keep it secure. In a moment, you’ll store it as an environment variable rather than embedding it directly in your code.

To call multiple AI models from a single Python script, you’ll use OpenRouter’s API. You’ll use the requests library to make HTTP calls, which gives you full control over the API interactions without requiring a specific SDK. This approach works with any HTTP client and keeps your code simple and transparent.

First, create a new directory for your project and set up a virtual environment. This isolates your project dependencies from your system Python installation:

$ mkdir openrouter-project/
$ cd openrouter-project/
$ python -m venv venv/

Now, you can activate the virtual environment:

• Windows
• Linux + macOS

PS> venv\Scripts\activate

$ source venv/bin/activate

You should see (venv) in your terminal prompt when it’s active. Now you’re ready to install the requests package for conveniently making HTTP calls:

(venv) $ python -m pip install requests

Now, gather the API key you created before and set it as an OPENROUTER_API_KEY environment variable in your terminal session: