The development stage is designed for local development. It includes debug tools, dev dependencies, and is configured for live code reloading.
# --- Stage 3: Dev Environment ---
FROM python_base AS dev
COPY --from=ghcr.io/astral-sh/uv:latest /uv /uvx /bin/
# Add common debug tools for local troubleshooting
RUN apk add --no-cache \
curl \
git \
vim \
wget \
bind-tools \
netcat-openbsd \
procps
WORKDIR /app
COPY --from=builder /app/.venv /app/.venv
ENV PATH="/app/.venv/bin:$PATH"
ENV PYTHONPATH="/app/src"
COPY pyproject.toml uv.lock ./
RUN --mount=type=cache,target=/root/.cache/uv \
uv sync --frozen --no-install-project
CMD ["fastapi", "dev", "src/blazing/main.py", "--host", "0.0.0.0", "--port", "8000"]Breaking It Down
Debug tools — Utilities like curl, git, and vim are installed for troubleshooting inside the running container. These would never be included in a production image.
Copying the virtual environment from builder — The line COPY --from=builder /app/.venv /app/.venv pulls the pre-built virtual environment from the builder stage. This already contains all production dependencies.
Installing dev dependencies — Running uv sync again (without --no-dev) adds development dependencies on top of the existing virtual environment. Since production deps are already installed, this only adds what's missing.
FastAPI dev mode — The fastapi dev command starts the application with auto-reload enabled. When source files change, the server automatically restarts.
No Source Code
Notice that the source code is not copied into this image. Instead, the source directory will be mounted as a volume at runtime. This enables live reloading—changes made on the host are immediately reflected in the container without rebuilding.