Database created empty when models are in a separate file?

Question

I am reading a book about flask development, and I'm pretty new to python generally.

File layout:

Project
|
|-- App
|   |-- __init__.py
|   |-- models.py
|
| main.py

Code inside __init__.py:

from flask import Flask
from flask.ext.bootstrap import Bootstrap
from flask.ext.sqlalchemy import SQLAlchemy
import os
from config import options

basedir = os.path.abspath(os.path.dirname(__file__))
bootstrap = Bootstrap()
db = SQLAlchemy()

def create_app():   
    app = Flask(__name__)
    app.config['SQLALCHEMY_DATABASE_URI'] =\
        'sqlite:///' + os.path.join(basedir, 'database_test.sqlite')

    bootstrap.init_app(app)
    db.init_app(app)

    with app.app_context():
            db.create_all()
            print("DB created")

    return(app)

I have been researching other people's issues on the site, mostly here where I found to use the with app.app_context(), and to instantiate the db without using app as part of the constructor.

Here is my models.py file:

from . import db


class User(db.Model):
    __tablename__ = 'Users'
    account_id = db.Column(db.Integer, primary_key=True)
    personaname = db.Column(db.String(50), unique=False)
    steamid = db.Column(db.String(64))
    avatar = db.Column(db.String(200))
    profileurl = db.Column(db.String(128))
    is_personaname_real = db.Column(db.Integer)

    def __repr__(self):
        return '<User {0}>'.format(self.personaname)

I then rune the code from main.py which is just:

from app import create_app

app = create_app()

If I move the User class into the __init__.py function, everything is created fine. However, when the User class is inside it's own file, the database is created empty. I have tried using other ways of importing, maybe something like From app.__init__.py Import db, but that didn't work either.

You need to import your models. The classes aren't created, and as a result not registered with SQLAlchemy, until you do. — dirn
– dirn, Commented May 8, 2015 at 13:16
I tried adding from . import models to the import lists in __init__.py, but now It gave these errors: here I know I imported wrong but how should I import the models? — k4kuz0
– k4kuz0, Commented May 8, 2015 at 13:22
plus if you look at THIS stack overflow question, the answer did not require importing the models, unless I'm looking wrong? — k4kuz0
– k4kuz0, Commented May 8, 2015 at 13:38
You have a circular import. __init__ is importing your models, which import db, before db is combined. Define db before the import. — dirn
– dirn, Commented May 8, 2015 at 13:48
That question already had the models imported so it required a different answer. — dirn
– dirn, Commented May 8, 2015 at 13:49

Community · Accepted Answer · 2017-05-23 12:06:32Z

2

Since defining your model directly in __init__.py works, it follows that you need to import your model(s) into __init__.py.

You can add an import in __init__.py after you create an SQLAlchemy object:

db = SQLAlchemy()
from .models import User

This works, but it feels horribly wrong and dirty to me. I don't know Flask that well, but this answer suggests that this is normal for Flask: https://stackoverflow.com/a/19008403/21945

edited May 23, 2017 at 12:06

CommunityBot

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answered May 8, 2015 at 13:48

mhawke

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3 Comments

dirn Over a year ago

There are a few common application layouts. Some require things like this to avoid circular imports. Some don't. The OP's layout falls into the former.

k4kuz0 Over a year ago

Thanks for your answer. How and when were the models imported in this answer? Because as far as I can see, theirs ended up working fine without having to import after the instantiation of db.

k4kuz0 Over a year ago

You were right about having to import the Models. I imported them into my main.py with the line from app.models import user

nadermx · Accepted Answer · 2015-05-08 13:03:59Z

0

This should work, seem you are missing the if statement

from app import create_app

app = create_app()

if __name__ == "__main__":
    app.run()

answered May 8, 2015 at 13:03

nadermx

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1 Comment

k4kuz0 Over a year ago

Database is still empty when running.

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