CherryPy Hello World

1 Introduction to CherryPy

CherryPy is a Python web framework that feels more like a library than a framework. You define a class, map URLs to methods, and it handles HTTP under the hood. It’s small, fast, and unopinionated—ideal for small services, internal tools, or any project that doesn’t need the ceremony of a heavier stack.

Key points:

Minimal setup: No ASGI/WSGI ceremony for basic apps.
Pythonic: Plain classes + methods for routes.
Extensible: Add plugins and tools as needed.
Battle-tested: Longstanding project with a solid history.

Click "Next" to set up your environment and write a working Hello World.

2 Prerequisites

You’ll need Python 3.8 or newer and pip. Check your version:

python --version

If you don’t have Python installed, grab it from python.org.

3 Install CherryPy

Create a virtual environment and install CherryPy.

python -m venv .venv
# Activate it:
# macOS/Linux
source .venv/bin/activate
# Windows
.venv\Scripts\activate

Install CherryPy:

pip install cherrypy

4 Create app.py

Make a file called app.py with the following code:

import cherrypy

class HelloWorld:
    @cherrypy.expose
    def index(self):
        return "Hello, world! This is CherryPy."

if __name__ == "__main__":
    cherrypy.tree.mount(HelloWorld(), "/")
    # Optional: quick dev config; remove or adapt for production
    cherrypy.config.update({
        "engine.autoreload.on": True,
        "log.screen": True,
        "server.socket_host": "127.0.0.1",
        "server.socket_port": 8080
    })
    cherrypy.engine.start()
    cherrypy.engine.block()

Save the file. Next, you’ll run it locally.

5 Run Locally

Start the server:

python app.py

Visit http://127.0.0.1:8080/. You should see the greeting.

6 Extra Route and a Query Param

Add a new method to app.py and expose it. This shows query parameter handling:

import cherrypy

class HelloWorld:
    @cherrypy.expose
    def index(self):
        return "Hello, world! This is CherryPy."

    @cherrypy.expose
    def greet(self, name="friend"):
        return f"Hello, {name}!"

if __name__ == "__main__":
    cherrypy.tree.mount(HelloWorld(), "/")
    cherrypy.config.update({
        "engine.autoreload.on": True,
        "log.screen": True,
        "server.socket_host": "127.0.0.1",
        "server.socket_port": 8080
    })
    cherrypy.engine.start()
    cherrypy.engine.block()

Restart the server. Try /greet?name=world or /greet?name=April.

7 Wrap-up and Next Steps

You now have a working CherryPy service—small, readable, and quick to iterate. From here, you can add static assets, sessions, JSON endpoints, or plug in a production-ready server.

Static files with tools.staticdir.root and tools.staticdir.dir.
JSON responses by returning a dict from a method and enabling cherrypy.tools.json_out.
Production server: deploy behind a reverse proxy (nginx) and run via systemd or a process manager.

Next, try building a small API or pairing CherryPy with a frontend for a simple app-like experience.

Tutorial Progress