Basic Flask SQLAlchemy Context Issue - python-3.x

Question

I've read many of the other posts on having models separated from the main app but I can't get it to work with just app.py (my actual app) and models.py (my database models).
If I do the following I get an app.db file with no tables:
from app import db
db.create_all()
If I do the following I get a RuntimeError: No application found. Either work inside a view function or push an application context.:
from app import db
db.create_all()
I have also looked at Introduction into Contexts page and can't work out where I put def create_app():, none of it seemed to work in my case.
Here is my app.py:
from flask import Flask, render_template, request
from flask_sqlalchemy import SQLAlchemy
from models import userTable
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)
#app.route('/', methods=['GET', 'POST'])
def home():
return "home"
if __name__ == '__main__':
app.run(debug=True)
Here is my models.py:
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
class userTable(db.Model):
__tablename__ = "userTable"
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True)

Answer 1

Perhaps you could try the following:
app.py
from flask import Flask, render_template, request
from flask_sqlalchemy import SQLAlchemy
import models
from models import initialize_db
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///app.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
initialize_db(app)
#app.route('/', methods=['GET', 'POST'])
def home():
return "home"
if __name__ == '__main__':
app.run(debug=True)
models.py
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
def initialize_db(app):
app.app_context().push()
db.init_app(app)
db.create_all()
class userTable(db.Model):
__tablename__ = "userTable"
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True)
The key is creating a database initialization function within models.py which takes the application instance as a parameter. This function only creates the database tables once it has its application instance. This will allow you to import the models module initially without an application instance and still have a modular design.