Python Tutorial

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.

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"

Create a Python project

Create a subdirectory and name it app. Add the following to it:

Save the following sample script as a new main.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

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.

Review the project directory

Your project directory should now look like this:

your-project-root/
├── docker-compose.yml
└── app/
    ├── Dockerfile
    ├── main.py
    └── requirements.txt

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

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.

Clean up

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

docker compose down

Building Secure Apps

Tutorials

K8s Guides

TLS Guides

Troubleshooting

Debugging