Python
Cloudflare Workers provides first-class support for Python, including support for:
- The majority of Python’s Standard library
- All bindings, including Workers AI, Vectorize, R2, KV, D1, Queues, Durable Objects, Service Bindings and more.
- Environment Variables, and Secrets
- A robust foreign function interface (FFI) that lets you use JavaScript objects and functions directly from Python — including all Runtime APIs
- Built-in packages, including FastAPI, Langchain, httpx and more.
Get started
A Python Worker can be as simple as three lines of code:
Similar to Workers written in JavaScript, TypeScript, or Rust, the main entry point for a Python worker is the fetch handler. In a Python Worker, this handler is named on_fetch.
To run a Python Worker locally, you use Wrangler, the CLI for Cloudflare Workers:
To deploy a Python Worker to Cloudflare, run wrangler deploy:
Modules
Python workers can be split across multiple files. Let’s create a new Python file, called src/hello.py:
Now, we can modify src/entry.py to make use of the new module.
Once you edit src/entry.py, Wrangler will automatically detect the change and
reload your Worker.
The Request Interface
The request parameter passed to your fetch handler is a JavaScript Request object, exposed via the foreign function interface, allowing you to access it directly from your Python code.
Let’s try editing the worker to accept a POST request. We know from the
documentation for Request that we can call
await request.json() within an async function to parse the request body as
JSON. In a Python Worker, you would write:
Once you edit the src/entry.py, Wrangler should automatically restart the local
development server. Now, if you send a POST request with the appropriate body,
your Worker should respond with a personalized message.
The env Parameter
In addition to the request parameter, the env parameter is also passed to
the Python fetch handler and can be used to access
environment variables,
secrets,and
bindings.
For example, let’s try setting and using an environment variable in a Python
Worker. First, add the environment variable to your Worker’s wrangler.toml:
Then, you can access the API_HOST environment variable via the env parameter:
Further Reading
- Understand which parts of the Python Standard Library are supported in Python Workers.
- Learn about Python Workers’ foreign function interface (FFI), and how to use it to work with bindings and Runtime APIs.
- Explore the Built-in Python packages that the Workers runtime provides.