In this tutorial, we will build a custom Python app using Docker Compose and a multi-stage Dockerfile. The build stage uses latest-dev because it requires the package installer pip. The runtime stage uses the fully distroless image to achieve the most secure app.
1

Create Docker Compose file

Create a project directory and save the code below to a new docker-compose.yml file:
services:
  flask-app:
    build: ./app
    ports:
      - "5000:5000"
2

Create a Python project

Create a subdirectory and name it app. Add the following to it:
  • Save the following sample script as a newmain.py file. 
    from flask import Flask
from datetime import datetime

app = Flask(__name__)

@app.route("/")
def show_time():
    now = datetime.now()
    return f"Current date and time: {now.strftime('%Y-%m-%d %H:%M:%S')}"

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=5000)
  • Save a requirements.txt file to list the Python packages that the project depends on. Python’s default package installer pip uses it. For our simple example, save only: 
    flask>=3.1.1
3

Create the Dockerfile

In the same directory, save the code below to a new Dockerfile:
# === Build Stage ===
FROM reg.mini.dev/python:latest-dev as builder

WORKDIR /app

RUN python -m venv venv
ENV PATH="/app/venv/bin":$PATH
COPY requirements.txt requirements.txt
RUN pip install -r requirements.txt

# === Runtime Stage ===
FROM reg.mini.dev/python:latest

WORKDIR /app

COPY main.py main.py
COPY --from=builder /app/venv /app/venv
ENV PATH="/app/venv/bin:$PATH"

ENTRYPOINT ["python", "main.py"]
Note that the builder stage uses reg.mini.dev/python:latest-dev so it can utilize PIP. The runtime stage uses the fully distroless production image - reg.mini.dev/python:latest .
4

Review the project directory

Your project directory should now look like this:
your-project-root/
├── docker-compose.yml
└── app/
    ├── Dockerfile
    ├── main.py
    └── requirements.txt
5

Authenticate to the Minimus registry

Before building the app, authenticate to the Minimus registry using your Minimus token:
docker login reg.mini.dev -u minimus -p {pull-token}
6

Build the app

You are now ready to build the app using Docker Compose:
docker compose build
Docker Compose will build the app from the app folder. Once built, you will see a confirmation:
✔ flask-app  Built
7

Run and test the app

Run the app:
docker compose up
Test the app by sending it a request:
curl http://127.0.0.1:5000
You should get a response with the current date and time.
8

Clean up

Once ready to clean up, run the following command to remove the container:
docker compose down