ImportError: attempted relative import beyond top-level package FastAPI

Question

I recently started working with FastAPI and faced such a problem. My project structure:

My_Project
└───backend
    │   alembic.ini
    │   sqlite.db
    │   requirements.txt
    │
    ├───alembic
    │   │   env.py
    │   │   script.py.mako
    │   │
    │   └───versions
    │           2023-02-22_added_users_tables.py
    │           __init__.py
    │
    └───app
        │   database.py
        │   main.py
        │   __init__.py
        │
        └───users
                models.py
                router.py
                schemas.py
                __init__.py

I am trying to import Base from database.py, being in models.py:

#models.py
from ..database import Base

And when I try to run the server I get this error:

ImportError: attempted relative import beyond top-level package

I have worked with Django before and have never encountered such errors.

I have looked at several similar questions and answers to them, but I have not figured out how to solve this problem.

I tried to use absolute import:

from app.database import Base

or

from backend.app.database import Base

but I got this error:

ModuleNotFoundError: No module named 'app' # And in the second case: 'backend'

Answer 1

You're going to have to launch your server from outside the folder it's in, or edit the cwd. Then, append your path to import the external files.

You also need and __init__.py in each of the external directories.

Here's a working solution from one of my projects:

main.py

import sys

from fastapi import FastAPI
from pathlib import Path

external_path = Path.cwd() / 'external_dir'
sys.path.insert(1, str(external_path))

import external_module

app = FastAPI()

run_server.py (or you can do this in VSCode's launch.json)

import uvicorn

if __name__ == "__main__":
    uvicorn.run("app:main", host="127.0.0.1", port=8000, reload=True, log_level="debug", reload_dirs=["app", "exernal_dir"])

or with launch.json

{
  "configurations": [
    {
      "name": "Python: debug",
      "type": "python",
      "request": "launch",
      "module": "uvicorn",
      "args": [
        "--host=0.0.0.0",
        "--port=8000",
        "--reload",
        "--log_level=debug",
        "--reload-dir=app",
        "--reload-dir=external_dir",
        "--factory",
        "--workers=1",
        "app:main"
      ],
      "jinja": false,
      "justMyCode": false
    }
  ]
}

Then from your root dir, run python my_app/run_server.py

---

Project structure would look like this:

my_app/
    /external_dir
        __init__.py
        external_module/
            __init__.py
            external.py

    /app
        __init__.py
        main.py
        
    /run_server.py