How to avoid reinstalling packages when building Docker image for Python projects?

Question

My Dockerfile is something like

FROM my/base

ADD . /srv
RUN pip install -r requirements.txt
RUN python setup.py install

ENTRYPOINT ["run_server"]
         


        

Answer 1

I found that a better way is to just add the Python site-packages directory as a volume.

services:
    web:
        build: .
        command: python manage.py runserver 0.0.0.0:8000
        volumes:
            - .:/code
            -  /usr/local/lib/python2.7/site-packages/

This way I can just pip install new libraries without having to do a full rebuild.

EDIT: Disregard this answer, jkukul's answer above worked for me. My intent was to cache the site-packages folder. That would have looked something more like:

volumes:
   - .:/code
   - ./cached-packages:/usr/local/lib/python2.7/site-packages/

Caching the download folder is alot cleaner though. That also caches the wheels, so it properly achieves the task.