Running the server with Uvicorn

Uvicorn is an ASGI server. It runs your FastAPI app object and listens on a host and port.

Command line

From the directory that can import your module:

uvicorn app:app --host 0.0.0.0 --port 8000 --reload

• First app: Python module name (e.g. app.py → app).
• Second app: variable holding the FastAPI() instance.

--reload restarts on file changes (development only).

In Python (programmatic startup)

You can start Uvicorn from code instead of the CLI:

import uvicorn
from fastapi import FastAPI

app = FastAPI()

def run(port: int = 5050) -> None:
    config = uvicorn.Config(app=app, host="0.0.0.0", port=port, log_level="info")
    server = uvicorn.Server(config=config)
    server.run()

if __name__ == "__main__":
    run()

Use this when your rubric asks for python app.py instead of the uvicorn CLI.

Threading note (advanced)

Some applications run Uvicorn in a background thread next to other code. For this course, run only Uvicorn in the foreground for labs unless your instructor assigns threading.

Check it

1. Start the server.
2. Visit http://127.0.0.1:8000/docs for interactive OpenAPI docs (FastAPI feature).
3. curl http://127.0.0.1:8000/ping should show {"message":"pong"}.

Implement

1. Document in README.md the exact command to start your app (or python ... entry).
2. Verify /ping from browser or curl / HTTPX.
3. Commit and push.