How can I properly annotate types using flask_sqlalchemy?

user_562769 0
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I have a working Flask application which uses SQLAlchemy / flask_sqlalchemy. To give you an impression, I've created a super stripped down version (apps.py and models.py). The application works. The issue is that mypy complains about the usage of db.Model within models.py:

error: Name 'db.Model' is not defined

The reason is likely that this is created when db.init_app(app) is called. How can I fix this? Is there a better option than ignoring it?

# type: ignore

app.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()

def create_app():
    app = Flask(__name__, template_folder="templates")
    db.init_app(app)
    return app

models.py

from app import db

class User(db.Model):
    __tablename__ = "users"
    id = db.Column(db.String, primary_key=True, nullable=False)
    username = db.Column(db.String, unique=True)
python-typing flask-sqlalchemy mypy flask sqlalchemy
2 Answers
user_65157550

Since you are using flask_sqlalchemy, Have you tried this,

models.py

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db'
db = SQLAlchemy(app)


class User(db.Model):
    __tablename__ = "users"
    id = db.Column(db.String, primary_key=True, nullable=False)
    username = db.Column(db.String, unique=True)

EDIT This is how my app.py looks like

from .settings import ProdConfig


def create_app(config_object=ProdConfig):
    app = Flask(__name__)
    app.config.from_object(config_object)
    register_blueprints(app)
    return app
user_41710460
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