ModuleNotFoundError and import errors in Docker container

Question

When importing python modules locally, I am able to successfully do so, however I'm having difficulty doing so when dockerising the app. It seems as though I get the opposite behaviour locally to how I get in the docker app... any thoughts?

I have the following directory structure

| app
|      |api.py
|      |settings.py
| tests
|      |test_api.py

In api.py, I import settings by: from app import settings In test_api.py I import app.py by: from app import api.

Locally, everything works fine. When I try to dockerize this API using the following Dockerfile:

FROM python:3.8.5-alpine

RUN pip install pipenv
COPY Pipfile /usr/src/
WORKDIR /usr/src
RUN pipenv lock --requirements > requirements.txt
RUN pip install -r requirements.txt

COPY app /usr/src/app

WORKDIR /usr/src/app

CMD ["python", "api.py"]

The docker image builds successfully, however upon running the container, I get the following error:

File "api.py", line 4, in <module>
from app import settings
ModuleNotFoundError: No module named 'app'

If I change how I import in api.py, to import settings, I get errors locally, but the docker container works perfectly. I'm pretty sure it's something to do with the PythonPath, any thoughts on how I can resolve this?

i believe that if you try to use it as a module, i'd recommend you to create a file init.py on the app folder... it is required to make Python treat directories containing the file as packages.(can just be an empty file) — lhd
– lhd, Commented Nov 6, 2020 at 12:58
I've answered the question in one of the responses below after having seen some other posts online and combining them with the answer from @stefan below. — Anish Patel
– Anish Patel, Commented Nov 6, 2020 at 13:33

Anish Patel · Accepted Answer · 2020-11-06 13:32:49Z

10

I've just come across another thread on StackOverflow which seems to have resolved my issue. I can leave the import statements as I indicated above in my question, and by setting the PYTHONPATH in the docker container correctly, I am able to get the imports working correctly in docker.

How do you add a path to PYTHONPATH in a Dockerfile

My updated (working) Dockerfile is as follows:

FROM python:3.8.5-alpine

RUN pip install pipenv
COPY Pipfile /usr/src/
WORKDIR /usr/src
RUN pipenv lock --requirements > requirements.txt
RUN pip install -r requirements.txt

COPY app /usr/src/app

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

CMD ["python", "app/api.py"]

answered Nov 6, 2020 at 13:32

Anish Patel

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1 Comment

Anurag Verma Over a year ago

How to write when I have multiple such apps like app1, app2, app3, etc: ` | app1 | |api.py | |settings.py |app2 | |x.py | |y.py |app3 | |alpha.py | tests | |test_api.py `

Stefan xyz · Accepted Answer · 2020-11-06 12:59:03Z

1

Your working directory is /usr/src/app and the import statement tries to find the directory "app". If you change your working directory to /usr/src/.

Alternatively you can import the settings directly via:

import settings

instead of

from app import settings

answered Nov 6, 2020 at 12:59

Stefan xyz

311 bronze badge

3 Comments

Anish Patel Over a year ago

Changing the WORKDIR to usr/src doesn't solve the problem as is I do that, it can't find api.py. If I then have the CMD["python", "app/api.py"], I get exactly the same problem. Using the import settings as opposed to from app import settings works in the docker container, but not locally.

Anish Patel Over a year ago

Looks like I need the WORKDIR to /usr/src as well as some other bits which I'll add in a separate post.

Stefan xyz Over a year ago

@AnishPatel from where do you start your api.py locally? if its from outside app you could use "from . import settings"

Rajan · Accepted Answer · 2020-11-06 13:08:03Z

-1

You should use just

import settings

since, "api.py" & "settings.py" both are in app folder.

edited Nov 6, 2020 at 13:08

answered Nov 6, 2020 at 12:59

Rajan

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4 Comments

Anish Patel Over a year ago

This works for the docker container, but then I get local issues... perhaps some local python path stuff? I'm using Pipenv which potentially complicates matters.

Rajan Over a year ago

I am not getting your question. Are you trying to say that you are doing the same project on docker & also locally?

Rajan Over a year ago

what is file hierachy for local project?

Anish Patel Over a year ago

The file hierarchy is the same locally as in the docker container. The solution is above, I've posted it. Thanks for looking.

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