Flask-migrate multiple models.py - flask

Question

I've a question related to Flask-migrate.
I'm creating a set of web services with Flask. I've split each web service in his own package in a python application.
The application structure look like this:
MyApp
WS1
models.py
WS2
models.py
CommonPackage
models.py
How can I import all the modules and init the db? I've tried to import them all manually but is not working.
I know that it works if I import the "app" from WS1 or Ws2 separately, but I would like to do this in a single operation, is this possible?
Here you can find the code for Flask-migrate:
#!virtualenv/bin/python
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate, MigrateCommand
from flask_script import Manager
from config import SQLALCHEMY_DATABASE_URI
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = SQLALCHEMY_DATABASE_URI
db = SQLAlchemy(app)
migrate = Migrate(app, db)
manager = Manager(app)
manager.add_command('db', MigrateCommand)
from WS1.models import Class1, Class2, Class3 <--- This is not importing
from WS2.models import Class4, Class5, Class6 <--- This is not importing
if __name__=='__main__':
manager.run()
This is the modules where I initialize SQLAlchemy session:
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session, sessionmaker
from sqlalchemy.ext.declarative import declarative_base
from config import SQLALCHEMY_DATABASE_URI
engine = create_engine(SQLALCHEMY_DATABASE_URI, convert_unicode = True)
db_session = scoped_session(sessionmaker(autocommit=False,
autoflush=False,
bind=engine))
Base = declarative_base()
Base.query = db_session.query_property()
All the models import this module and inherit from Base.
Thanks a lot,
Enrico

Answer 1

When you are defining a custom declarative base you're not really using Flask-SQLAlchemy anymore—and Flask-Migrate reads the models from Flask-SQLAlchemy's internal declarative base. (That is why you have to initialize Migrate with both app and db).
Flask has an answer to the import cycle problem: Most Flask extensions have an .init_app() method to defer initializing the extension where necessary.
In the module where you currently create Base by hand, just do db = SQLAlchemy() and then in your models import db and use db.Models as your declarative base instead of Base. In your app.py, do the following:
from dbpackagename import db
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = SQLALCHEMY_DATABASE_URI
db.init_app(app)