Post History

Different behavior with relative imports when using flask vs py

I have a small new Python 3.8 Flask project with some relative import quirks.

For the DB I use SQLAlchemy with Flask-Migrate. My project has the following general structure:

```
controllers/
static/
templates/
app.py
controller.py
helpers.py
models.py
requirements.txt
```

The app.py looks like this:

```python
from .controller import app

if __name__ == "__main__":
    app.run(host='0.0.0.0', port=5000, debug=True)
```

And the controller.py like this:

```python
from flask import Flask
from . import helpers

app = Flask(__name__)
app.config.update(dict(
    SQLALCHEMY_DATABASE_URI = "...",
    SQLALCHEMY_TRACK_MODIFICATIONS = "..."
))
db = SQLAlchemy(app)
migrate = Migrate(app, db)

from .controllers.static_controller import static

app.register_blueprint(static, url_prefix='/')
```

The import in the model is this:

```
from .controller import db
```

And for the controllers the import is like this:

```
from flask import Blueprint, render_template, url_for, abort
from ..models import *
```

Using this setup I can run the application with the command `flask run`. However (likely due to a configuration error), I cannot use the restarter in that mode, because it shows an error that the python interpreter can't be found.

Hence I thought about using `app.run` (as you can see in the app.py), which does work in my experience. However, when I start the app with `py app.py`, I get this error:

```
Traceback (most recent call last):
  File "app.py", line 2, in <module>
    from .controller import app
ImportError: attempted relative import with no known parent package
```

I tried adding an `__init__.py` to the working directory, but that didn't help either.

My question is: **How can I use relative imports here without drastically changing the project structure?**