8. Deploying

The same app.py runs in production:

$ python app.py --prod

Production mode serves everything from one origin: your pages at /, the JSON API under /api (with Swagger UI at /api/docs) and Rational’s own assets under /_rational. It turns off debug output, listens on $HOST and $PORT, and trusts X-Forwarded-* headers from your reverse proxy.

Point the database at a real server through the environment:

$ DATABASE_URL="postgresql+asyncpg://user:pass@db/guestbook" python app.py --prod

A container image:

FROM python:3.13-slim
WORKDIR /srv
COPY . .
RUN pip install --no-cache-dir "rational[db]" asyncpg
ENV RATIONAL_ENV=production
CMD ["python", "app.py", "--prod"]

Important

Live page state is kept in the server’s memory. Run one process per container, or enable sticky sessions when you run several.

Running and deploying covers the other options: any ASGI server, python -m rational, mounting inside an existing FastAPI app, sub-paths behind a proxy and Content Security Policy.

That’s it: you built, tested and shipped a full-stack app in Python. Explore the Examples next, from a CV site to a marketplace.