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Python isn’t covered by Raypacks yet, so Python Frames use the classic Paketo builder. Switch the Frame’s Builder to Paketo in Frame Settings if it’s not already. What Paketo needs from you:
  1. A requirements.txt (or Pipfile / pyproject.toml).
  2. A Procfile with a web: line that boots your server.
  3. Your server binds to 0.0.0.0 on the port you set in the Frame.
If those are in place, skip to Deploy.

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Quick start (Flask + Gunicorn)

mkdir hello-py && cd hello-py
app.py:
app.py
import os
from flask import Flask

app = Flask(__name__)

@app.route("/")
def root():
    return "Hello from Python on Nubo!"

if __name__ == "__main__":
    app.run(host="0.0.0.0", port=int(os.environ.get("PORT", 8080)))
requirements.txt:
requirements.txt
flask
gunicorn
Procfile:
Procfile
web: gunicorn --bind 0.0.0.0:${PORT:-8080} app:app
The ${PORT:-8080} binds PORT if you’ve set it as a Frame variable, otherwise it falls back to 8080. Nubo doesn’t propagate the Frame’s port setting into a PORT env var, so to run on a non-8080 port, add a PORT variable in Frame Settings and set the Frame’s port to match (or just hardcode the port here). Test locally: 
pip install -r requirements.txt
PORT=8080 gunicorn --bind 0.0.0.0:$PORT app:app

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Deploy

1

Push to GitHub

Commit app.py, requirements.txt, and Procfile. Push.
2

New Frame on Nubo

Hit + Frame in your Project, connect the repo.
3

Confirm the port

Match what your Procfile binds to.
4

Deploy

First build takes a minute or two while Paketo resolves dependencies.

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Pinning a Python version

Paketo picks a recent Python by default. To pin a version, add project.toml:
project.toml
[project]
id = "python-starter"
name = "Python Starter"
version = "1.0.0"

[[build.env]]
name = "BP_CPYTHON_VERSION"
value = "3.12.*"

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Things that trip people up

  • flask run in your Procfile. That’s the dev server. Use Gunicorn (or Uvicorn for async apps).
  • Binding to 127.0.0.1. Bind to 0.0.0.0 so Nubo’s router can reach your app.
  • Port mismatch. Nubo doesn’t inject the Frame’s port as PORT. Either hardcode the port your app binds or set a PORT variable in Frame Settings, and make sure the Frame’s port matches what the app binds.
  • No Procfile. Paketo needs a web: line to know what to launch.

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Raypacks support

Python is on the Raypacks roadmap. We’ll add a Python pack once we’re confident the build flow is fast and predictable. For now, Paketo is the path.