How to correctly install custom package in Docker with docker-compose?

Question

I am building a flask api and want to create a docker image of it. However, when I do docker-compose run (after build), it cannot find the module.

Error:

api_1  | Traceback (most recent call last):
api_1  |   File "app.py", line 6, in <module>
api_1  |     from api.classify.classify import get_prediction
api_1  | ModuleNotFoundError: No module named 'api'

My folder structure looks like this:

- api
-- classify
--- classify.py
-- app.py
-- Dockerfile
-- requirements.txt
-- setup.py

The setup.py looks like this:

from setuptools import setup, find_packages


setup(
    name='image_api',
    keywords='',
    version='0.1',
    packages=find_packages()
)

And the Dockerfile looks like this:

FROM python:3
WORKDIR /user/src/app
ENV PYTHONPATH=/api
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt
COPY . .
RUN python setup.py install
CMD ["python", "app.py"]

How do I fix this and what is best practice to install custom packages when building a Docker image?

Answer 1

You should never over-write PYTHONPATH like that, nstead append your path, or the system will not find the installed Python packages.

You can do either of the following to make it work:

1. RUN export PYTHONPATH="$PYTHONPATH:/api"
2. ENV PYTHONPATH="$PYTHONPATH:/api"

Also your Dockerfile should be on api level, it wont be able to look for it in the present directory structure.