```markdown
# Dockerfile Source Code
```dockerfile
# Use a multi-stage build for better efficiency and security
# Stage 1: Builder
FROM python:3.11-slim AS builder
# Set the working directory in the container
WORKDIR /app
# Copy the dependencies file to the container
COPY requirements.txt .
# Install the dependencies
RUN pip install --no-cache-dir -r requirements.txt
# Stage 2: Runner
FROM python:3.11-slim
# Set the working directory
WORKDIR /app
# Copy the installed dependencies from the builder stage
COPY --from=builder /usr/local/lib/python3.11/site-packages /usr/local/lib/python3.11/site-packages
# Copy the rest of the application code to the container
COPY . .
# Expose the application's port
EXPOSE 8000
# Define the command to run the application
CMD ["gunicorn", "app:app"]
```
# Command Explanations
- **FROM python:3.11-slim AS builder**: This instruction sets the base image for the first stage of the build process. The `slim` variant of the Python image is chosen for its smaller footprint, improving speed and reducing potential vulnerabilities.
- **WORKDIR /app**: Sets the working directory inside the container. All subsequent commands will be executed relative to this path.
- **COPY requirements.txt .**: Copies the `requirements.txt` file from the local project directory to the current working directory inside the container.
- **RUN pip install --no-cache-dir -r requirements.txt**: Installs the Python dependencies specified in `requirements.txt`. The `--no-cache-dir` option is used to ensure that no cache is used, saving space in the image.
- **FROM python:3.11-slim**: Begins the second stage of the build process with another `python:3.11-slim` base image, aimed specifically at running the application.
- **COPY --from=builder /usr/local/lib/python3.11/site-packages /usr/local/lib/python3.11/site-packages**: Copies the installed Python packages from the builder stage to the runner stage.
- **COPY . .**: Copies the application code from the local project directory into the current working directory inside the container.
- **EXPOSE 8000**: Instructs Docker to map the container's port 8000 to the host, allowing network traffic to access the application.
- **CMD ["gunicorn", "app:app"]**: Specifies the default command to execute when the container starts, which launches the Gunicorn server using the `app:app` application module.
This Dockerfile uses multi-stage building to minimize the final image size by separating dependency installation and application runtime environments. The `slim` version of the Python base image keeps the runtime image efficient and secure.