Python with FastAPI and Flask

Python APIs are deployed from a GitHub Repository with the Python runtime (3.11, 3.12, or 3.13). Zenifra installs dependencies with pip install -r requirements.txt and starts the app with the start command.

Prerequisites

• requirements.txt at the repository root, with pinned versions
• A production server (uvicorn or gunicorn) listed in requirements.txt
• GitHub account connected to Zenifra

Generate the file from your virtual environment:

pip freeze > requirements.txt

Using Poetry or uv? Export to requirements.txt before committing: poetry export -f requirements.txt --output requirements.txt or uv export --format requirements-txt > requirements.txt.

FastAPI

from fastapi import FastAPI

app = FastAPI()

@app.get("/")
def root():
    return {"message": "Hello from Zenifra"}

@app.get("/health")
def health():
    return {"status": "ok"}

fastapi==0.115.0
uvicorn[standard]==0.30.6

To run more than one process per instance, use uvicorn workers under gunicorn:

start: gunicorn main:app -k uvicorn.workers.UvicornWorker --bind 0.0.0.0:8000 --workers 2

Add gunicorn to requirements.txt. Start with 2 workers and tune for the plan's memory: each worker loads its own copy of the app.

Behind the HTTPS proxy

Zenifra terminates HTTPS before forwarding the request. For URLs generated by FastAPI to use https, add --proxy-headers --forwarded-allow-ips="*" to uvicorn.

Flask

from flask import Flask

app = Flask(__name__)

@app.get("/")
def root():
    return {"message": "Hello from Zenifra"}

@app.get("/health")
def health():
    return {"status": "ok"}

flask==3.0.3
gunicorn==23.0.0

If the app uses the application factory pattern, point to the function: gunicorn "app:create_app()" --bind 0.0.0.0:8000.

Migrations with Alembic

Project variables, including DATABASE_URL, exist at runtime. Apply migrations before starting the server:

start: alembic upgrade head && uvicorn main:app --host 0.0.0.0 --port 8000

With Flask-Migrate, use flask db upgrade && gunicorn app:app --bind 0.0.0.0:8000.

Logs

Everything the app writes to stdout and stderr shows up in the project logs. Python output is already unbuffered, so print() and logging appear immediately. For gunicorn access logs, add --access-logfile -.

Projects with pyproject.toml

If the repository has pyproject.toml or setup.py, the package is also installed after the build. Even so, keep requirements.txt with every runtime dependency.

Common problems

Next steps

• Django
• Quickstart with a database
• Runtimes
• Framework guides