[Python] How to set up docker compose with django and pdm

I have a django project with pdm and docker compose and I set up the codebase volume to enable django hot reload and debugging in the container. Building with the compose config works fine but when I try to run the server with docker compose up -d I hit a python error as if the libs were not picked up properly.

The project has the following architecture

project/
├── config/
│ ├── settings.py
│ └── urls.py
│ └── ...
├── some_django_app/
│ └── ...
├── compose.yaml
├── Dockerfile
├── README.md
├── pyproject.toml
└── pdm.lock


the compose file is as follows

services:
web:
build:
dockerfile: Dockerfile

command: pdm run python manage.py runserver 0.0.0.0:8000
ports:
- 8000:8000
volumes:
- .:/app
env_file:
- .env


my dockerfile is as follows

# Use an official Python runtime as a parent image
FROM python:3.13.2-slim-bullseye

# Set environment variables
ENV PYTHONDONTWRITEBYTECODE=1
ENV PYTHONUNBUFFERED=1

# Set the working directory in the container
WORKDIR /app

# Install system dependencies
RUN apt-get update && apt-get install -y \
build-essential \
libpq-dev \
&& rm -rf /var/lib/apt/lists/*

# Install PDM
RUN pip install --no-cache-dir pdm

# Copy the project files into the container
COPY . /app

# Accept build argument for ENVIRONMENT
ARG ENVIRONMENT=prod

# Install project dependencies using PDM
pdm install --prod --no-lock --no-editable;


Here is the trace of the error when I up the container

INFO: The saved Python interpreter does not exist or broken. Trying to find another one.
INFO: __pypackages__ is detected, using the PEP 582 mode
Traceback (most recent call last):
File "/app/manage.py", line 12, in main
from django.core.management import execute_from_command_line
ModuleNotFoundError: No module named 'django'

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
File "/app/manage.py", line 23, in <module>
main()
~~~~^^
File "/app/manage.py", line 14, in main
raise ImportError(
...<3 lines>...
) from exc
ImportError: Couldn't import Django. Are you sure it's installed and available on your PYTHONPATH environment variable? Did you forget to activate a virtual environment?


It is as if pdm couldn't pick up my local libs. When I remove the container line in my compose file and rebuild, django runs fine. What is wrong with my configuration?

Continue reading...