I can not run fastapi and pytest at the same time due to an import module error

Question

I'm having a circular problem that I'm not able to solve. I started my project as follows:

.
├── conf
│   ├── __init__.py
│   └── server.py
├── __init__.py
├── main.py
├── requirements.txt
└── tests
    ├── __init__.py
    └── v1
        ├── __init__.py
        └── test_item.py

In main.py I have:

from fastapi import FastAPI
import uvicorn

from conf.server import HOST, PORT

app = FastAPI()


@app.get("/")
async def root():
    return {"message": "Hello World"}

if __name__ == '__main__':
    uvicorn.run("main:app", host=HOST, port=PORT, reload=True)

In test_main.py

from fastapi.testclient import TestClient

from main import app

client = TestClient(app)


def test_read_main():
    response = client.get("/")
    assert response.status_code == 200
    assert response.json() == {"message": "Hello World"}

The error I get when I run the script from the same level as main.py with pytest:

C:\Python39\lib\importlib\__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests\v1\test_item.py:3: in <module>
    from main import app
E   ModuleNotFoundError: No module named 'main'

If I write the name of the folder before main:

from api.main import app

I get an error with the con/server.py module:

Hint: make sure your test modules/packages have valid Python names.
Traceback:
C:\Python39\lib\importlib\__init__.py:127: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests\v1\test_item.py:3: in <module>
    from api.main import app
main.py:4: in <module>
    from conf.server import HOST, PORT
E   ModuleNotFoundError: No module named 'conf'

If I now change in main to include the name of the folder:

from api.conf.server import HOST, PORT

The test finally works, but now If I try to run the server wiht python main.py it will not work anymore:

    from api.conf.server import HOST, PORT
ModuleNotFoundError: No module named 'api'

What I'm doing wrong to get into this loop?

Answer 1

Your should import your modules using absolute imports, as you already described in the final part of your question:

from api.main import app
from api.conf.server import HOST, PORT

and make sure to include the directory containing your package directory in PYTHONPATH, as shown here (Option 3). Then, you should be able to run your script. Other options listed in the above link might help you as well.

Answer 2

run

python -m main

instead of

python main.py