example init

__init__.py

from flask import Flask
from config import Config
from extensions import db

def create_app():
    app = Flask(__name__)
    app.config.from_object(Config)

    db.init_app(app)

    from views import author_bp
    app.register_blueprint(author_bp)

extensions.py

from flask.ext.mongoalchemy import MongoAlchemy

db = MongoAlchemy()

models.py

from extensions import db

class Author(db.Document):
    name = db.StringField()

class Book(db.Document):
    title = db.StringField()
    author = db.DocumentField(Author)
    year = db.IntField();