To package our project into a Docker container, we need an additional command: WORKDIR.

FROM python:3.9-slim

# Set the working directory inside the container
WORKDIR /flask-app

COPY . .
RUN pip3 install -r requirements.txt

# Set the command to run the Flask application
CMD [ "python3", "-m" , "flask", "run", "--host=0.0.0.0"]

The WORKDIR command in Docker sets the working directory for any subsequent instructions in the Dockerfile. In your case, WORKDIR /flask-app sets /flask-app as the working directory.

This means that any further instructions (such as COPY, RUN, CMD, etc.) will be executed in the context of this directory. For example, if you execute COPY app.py /flask-app, the file app.py will be copied into the /flask-app directory inside the container.

This is useful for organizing your project within the container and ensuring clarity about where operations are taking place within the Docker image.