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

I recommend the approach detailed in this article (section 2). He uses virtualenv so pip install stores all the python code, binaries, etc. under one folder instead of spread out all over the file system. Then it's easy to copy just that one folder to the final "production" image. In summary:

Compile image

• Activate virtualenv in some path of your choosing.
• Prepend that path to your docker ENV. This is all virtualenv needs to function for all future docker RUN and CMD action.
• Install system dev packages and pip install xyz as usual.

Production image

• Copy the virtualenv folder from the Compile Image.
• Prepend the virtualenv folder to docker's PATH

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