Python is not able to find the file base_functions because it was run from other folder.

You may want to change the working directory of in the Dockerfile:

WORKDIR /path/to/workdir

Setting the PYTHONPATH as such works but feels clumsy:

ENV PYTHONPATH "${PYTHONPATH}:/app/"

Using Docker's WORKDIR allows for a much cleaner solution:

FROM python:3.7

WORKDIR /code

RUN pip install fastapi uvicorn python-osc

EXPOSE 80

COPY app ./app

CMD ["uvicorn", "app.main:app", "--host", "0.0.0.0", "--port", "80"]

Note how the COPY statement changed.

Not sure if this is what you're asking but if you have Python libraries within the Docker image and you want to append them to an already-exisitng Pipfile, you can copy the requirements.txt file from the Docker container and then use pipenv to install them.

# In terminal session 1 run the container with the default shell in interactive mode. This way the container stays alive and we can copy the file from the container to the host
docker run -it --rm $USER/$IMAGE_NAME:1.0.0.XXXXX sh

# In terminal session 2
docker cp $CONTAINER_ID:/requirements.txt ./

# This will add the requirements from the text file into the Pipfile
pipenv install -r requirement.txt

# Sometimes requirements will get corrupted
pipenv clean

If using Visual Studio Code, reload window to refresh dependencies in Python interpreter.

Use Dockerfile to install python packages.

Dockerfile content

FROM python:3

RUN pip install --upgrade pip && \
    pip install aldryn_apphooks_config

$: docker build -t "web:python" .
Sending build context to Docker daemon  3.584kB
Step 1/2 : FROM python:3
 ---> 59a8c21b72d4
Step 2/2 : RUN pip install --upgrade pip &&     pip install aldryn_apphooks_config
 ---> Running in e16a679af3d8
.
.
.
.
Successfully built aldryn-apphooks-config django-treebeard djangocms-admin-style
Installing collected packages: pytz, Django, django-appdata, django-treebeard, django-classy-tags, django-sekizai, djangocms-admin-style, django-formtools, django-cms, aldryn-apphooks-config
Successfully installed Django-2.1.8 aldryn-apphooks-config-0.5.2 django-appdata-0.2.1 django-classy-tags-0.8.0 django-cms-3.6.0 django-formtools-2.1 django-sekizai-0.10.0 django-treebeard-4.3 djangocms-admin-style-1.3.0 pytz-2018.9
Removing intermediate container e16a679af3d8
 ---> 78ecd015d983
Successfully built 78ecd015d983
Successfully tagged web:python

Start the container and verify the package installion.

$ docker run -it web:python /bin/bash
root@1d1df7416b8a:/# pip freeze
aldryn-apphooks-config==0.5.2
Django==2.1.8
django-appdata==0.2.1
django-classy-tags==0.8.0
django-cms==3.6.0
django-formtools==2.1
django-sekizai==0.10.0
django-treebeard==4.3
djangocms-admin-style==1.3.0
pytz==2018.9