Cython to ELF multistage build Dockerfile

Dockerfile

# Inspired by:
#   https://pythonspeed.com/articles/faster-multi-stage-builds/

# Builder image
FROM python:3.7-slim as compile-image

# Install all cython and C toolchain
#   Save some space from the compile-image by apt-cleaning and deleting
RUN apt-get update
RUN apt-get install -y --no-install-recommends gcc cython3 python3-dev \
apt-get clean \
rm -rf /var/lib/apt/lists/*

WORKDIR /root
# ----
COPY main.py .
# ----

# Transpile 'main.py' to 'main.c'
RUN cython3 -3 --embed -o main.c main.py
# Compile 'main.c' to an 'main' ELF 
RUN gcc -Os -I /usr/include/python3.7m -o main main.c -lpython3.7m -lpthread -lm -lutil

# Use different image for runtime
FROM python:3.7-slim as runtime-image

# Create non-root user (Security First!)
RUN useradd --create-home appuser
WORKDIR /home/appuser
USER appuser

# Copy 'main' executable to a brand new Python3.7m image (it has to be linked against 'python3.7m')
COPY --from=compile-image /root/main .

# Use it as entrypoint
CMD [ "./main" ]

main.py

#!/usr/bin/env python3

# cython: language_level=3

print(1)

Building will produce a container of about 450MB which is the builder and one of ~ 180MB which is the runtime

$ docker build -t cython3-twostage:latest .
$ docker run -ti cython3-twostage:latest

This is cool... I see that python3-dev now installs 3.9 headers. I managed to get everything to work by updating everything to 3.9.

There's also some missing &&.

# Builder image
FROM python:3.9-slim as compile-image

# Install all cython and C toolchain
#   Save some space from the compile-image by apt-cleaning and deleting
RUN apt-get update
RUN apt-get install -y --no-install-recommends gcc cython3 python3-dev && \
apt-get clean && \
rm -rf /var/lib/apt/lists/*

WORKDIR /root
# ----
COPY main.py .
# ----

# Transpile 'main.py' to 'main.c'
RUN cython3 -3 --embed -o main.c main.py
# Compile 'main.c' to an 'main' ELF 
RUN gcc -Os -I /usr/include/python3.9 -o main main.c -lpython3.9 -lpthread -lm -lutil

# Use different image for runtime
FROM python:3.9-slim as runtime-image

# Create non-root user (Security First!)
RUN useradd --create-home appuser
WORKDIR /home/appuser
USER appuser

# Copy 'main' executable to a brand new Python3.7m image (it has to be linked against 'python3.7m')
COPY --from=compile-image /root/main .

# Use it as entrypoint
CMD [ "./main" ]