How do I reduce a python (docker) image size using a multi-stage build?

Question

I am looking for a way to create multistage builds with python and Dockerfile:

For example, using the following images:

1st image: install all compile-time requirements, and install all needed python modules

2nd image: copy all compiled/built packages from the first image to the second, without the compilers themselves (gcc, postgers-dev, python-dev, etc..)

The final objective is to have a smaller image, running python and the python packages that I need.

In short: how can I 'wrap' all the compiled modules (site-packages / external libs) that were created in the first image, and copy them in a 'clean' manner, to the 2nd image.

Answer 1

ok so my solution is using wheel, it lets us compile on first image, create wheel files for all dependencies and install them in the second image, without installing the compilers

FROM python:2.7-alpine as base

RUN mkdir /svc
COPY . /svc
WORKDIR /svc

RUN apk add --update \
    postgresql-dev \
    gcc \
    musl-dev \
    linux-headers

RUN pip install wheel && pip wheel . --wheel-dir=/svc/wheels

FROM python:2.7-alpine

COPY --from=base /svc /svc

WORKDIR /svc

RUN pip install --no-index --find-links=/svc/wheels -r requirements.txt

You can see my answer regarding this in the following blog post

https://www.blogfoobar.com/post/2018/02/10/python-and-docker-multistage-build