__ indicates / in file name

foo__app.py

# -*- coding: utf-8 -*-

from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

import os
from flask import Flask
from flask.ext.sqlalchemy import SQLAlchemy

db = SQLAlchemy()


def create_app():
    app = Flask(__name__)
    app.config.from_object(get_conf())
    db.init_app(app)
    return app


def get_conf():
    local_settings_found = os.path.exists(
        os.path.join(os.path.dirname(__file__), 'config', 'local.py')
    )
    default_env = 'local' if local_settings_found else 'base'
    env = os.environ.get('FOO_SETTINGS', default_env)
    return 'foo.config.%s.Configuration' % env

foo__models__user.py

# -*- coding: utf-8 -*-

from __future__ import (absolute_import, division, print_function,
                        unicode_literals)

from datetime import datetime
from security.app import db


class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    msisdn = db.Column(db.String(20))
    email = db.Column(db.String(255), unique=True, nullable=False)
    password = db.Column(db.String(255), nullable=False)
    created = db.Column(db.DATETIME, default=datetime.utcnow, index=True)
    updated = db.Column(db.DATETIME, default=datetime.utcnow,
                        onupdate=datetime.utcnow, index=True)

python_session

>>> from foo.app import db
>>> db.metadata
MetaData(bind=None)
>>> db.metadata.__dict__
{'tables': immutabledict({}), '_schemas': set([]), '_bind': None, '_sequences': {}, 'quote_schema': None, 'schema': None}
>>>