Docker python not able to recognize custom module

Question

I have a project with the following structure:

project/
  checks/
    __init__.py
    <some files here>

  engine/
    __init__.py
    <some files here>

  models/
    __init__.py
    <some files here>

  __init__.py
  logger.py
  main.py
  requirements.txt
  Dockerfile

main.py looks something like this:

from project.logger import log

if __name__ == '__main__':
  <code>

If I run main.py, in my editor (PyCharm 2024.3), everything works fine. However, if I put everything in Docker, I get:

Traceback (most recent call last):
  File "/project/main.py", line 3, in <module>
    from project.logger import log
ModuleNotFoundError: No module named 'project'

My Dockerfile looks like this:

FROM python:3.13-alpine
WORKDIR /project
COPY ./requirements.txt /project/requirements.txt
RUN python -m pip install --no-cache-dir --upgrade pip
RUN pip install --no-cache-dir --upgrade -r /project/requirements.txt

COPY ./checks /project/checks
COPY ./engine /project/engine
COPY ./models /project/models

COPY ./__init__.py /project/__init__.py
COPY ./logger.py /project/logger.py
COPY ./main.py /project/main.py

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

Am I doing something wrong? Is there a way to force Python to recognize the module?

larsks · Accepted Answer · 2024-12-17 10:27:15Z

2

Am I doing something wrong?

Yes. If you try to import project, there needs to be either a file named project.py or a directory named project (that contains file __init__.py) somewhere in Python's search path (which includes the directory containing your script and standard locations like /usr/lib/python).

Since you are running your code from inside the project directory, the directory itself is effectively invisible to Python.

Instead of:

from project.logger import log

Write instead:

from logger import log

Python will find logger.py in the current directory and work as expected.

You can also dramatically simplify your Dockerfile:

FROM python:3.13-alpine

WORKDIR /project

# Install dependencies
COPY ./requirements.txt ./
RUN python -m pip install --no-cache-dir --upgrade pip && \
  pip install --no-cache-dir --upgrade -r requirements.txt

# Install application code
COPY . ./

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

answered Dec 17, 2024 at 10:27

larsks

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3 Comments

EntangledLabs Dec 17, 2024 at 18:01

thanks for the answer! question, why does this work in my local environment if u say it is invisible? supposedly it should work by your rules since the project/ directory has an init.py file, right?

larsks Dec 17, 2024 at 19:11

"supposedly it should work by your rules since the project/ directory has an init.py file, right". No, because you're running from inside the project directory. From the perspective of Python, there is no visible directory named project. It probably works with PyCharm because PyCharm is performing some magic for you (such as manipulating $PYTHONPATH).

EntangledLabs Dec 17, 2024 at 19:57

Ahh, that makes sense. I just tried it with main.py outside of the project/ directory and it worked perfectly, thanks!

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