Lesson 4 of 4
Docker & Containers
Concept
A container is a lightweight, isolated box that runs your app with all its dependencies. A Dockerfile is the recipe — what to install, what to copy, how to start. docker-compose.yml orchestrates multiple containers together.
m3shdup/Dockerfile
FROM python:3.12.9-slim # Start from a Python base image
WORKDIR /app # Set the working directory
COPY requirements.txt . # Copy deps list
RUN pip install -r requirements.txt # Install deps
COPY . . # Copy your code
CMD ["python", "run.sh"] # Start commandWhat's happening
Each line is a layer.
FROM picks the starting image. COPY puts your files in. RUN executes commands during build. CMD is what runs when the container starts. Docker caches unchanged layers — that's why requirements.txt is copied separately (deps don't change often, so that layer is cached).