My test Flask app main file

__init__.py

import click
from flask import Flask
from flask.cli import with_appcontext
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy.orm import DeclarativeBase

class Base(DeclarativeBase):
    pass

db = SQLAlchemy(model_class=Base)

@click.command("init-db")
@with_appcontext
def init_db_command():
    print("Initializing the database.")
    db.drop_all()
    db.create_all()


def create_app(test_config=None):
    app = Flask(__name__, instance_relative_config=True)
    app.config.from_mapping(
        SECRET_KEY="dev",
        SQLALCHEMY_DATABASE_URI="sqlite:///rmapp.sqlite"
    )

    db.init_app(app)
    app.cli.add_command(init_db_command)

    from . import page
    app.register_blueprint(page.bp)

    return app