On Wednesday, August 22, 2012 2:23:28 PM UTC+1, Simon King wrote: > > On Wed, Aug 22, 2012 at 12:51 PM, David McKeone > <davidm...@gmail.com<javascript:>> > wrote: > > I've been using SQLAlchemy with Flask via the Flask extension > > Flask-SQLAlchemy. Everything works great so far, but I foresee a > potential > > problem once I start to use my database model outside of Flask. In the > > future I'd like to be able to use my models with non-Flask SQLAlchemy (a > > worker daemon process or with a PySide interface). "Well just use > standard > > SQLAlchemy," you may say, " and fore-go the use of the extension". That > was > > my first thought, but sadly some useful extensions (notably > > Flask-DebugToolbar) seem to like using the extension version and it is > nice > > to be able to have Flask manage the database sessions in the way that it > > does. I'd like to not throw the baby out with the bath water. > > > > I realize that this is somewhat specific to Flask, but is there a way > that I > > could do both? Can I create models with standard SQLAlchemy declarative > and > > then somehow inject them into Flask-SQLAlchemy's way of doing things? > > > > If it helps with the solution, I don't need to use any of the Model > specific > > methods that Flask-SQLAlchemy provides (get_or_404, paginate, etc..) and > I > > also specify a __tablename__ for all of my models, so I don't rely on > > Flask-SQLAlchemy generating that for me. > > > > I took a look at the source of Flask-SQLAlchemy > > ( > https://github.com/mitsuhiko/flask-sqlalchemy/blob/master/flask_sqlalchemy.py) > > > > and from what I can tell it seems that it's using Flask's signalling > > capabilities by customizing SQLAlchemy's session and mapper, but that is > > where my understanding ends (I'm still new to this whole stack, Python, > > Flask, SQLAlchemy) and I could use some pointers for how to proceed. > > > > > > To visualize what I'm talking about, here are the two types of models. > A > > basic Flask-SQLAlchemy model looks like > > ( > http://packages.python.org/Flask-SQLAlchemy/quickstart.html#a-minimal-application): > > > > > > from flask import Flask > > from flask.ext.sqlalchemy import SQLAlchemy > > > > app = Flask(__name__) > > app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:////tmp/test.db' > > > > db = SQLAlchemy(app) > > > > class User(db.Model): > > id = db.Column(db.Integer, primary_key=True) > > username = db.Column(db.String(80), unique=True) > > email = db.Column(db.String(120), unique=True) > > > > def __init__(self, username, email): > > self.username = username > > > > self.email = email > > > > > > def __repr__(self): > > return '<User %r>' % self.username > > > > > > Note the db.Model, db.Integer and db <dot> everything. > > > > The plain declarative SQLAlchemy equivalent would be > > (http://flask.pocoo.org/docs/patterns/sqlalchemy/): > > > > > > from sqlalchemy import Column Integer, String, create_engine > > from sqlalchemy.orm import scoped_session, sessionmaker > > from sqlalchemy.ext.declarative import declarative_base > > > > engine = create_engine('sqlite:////tmp/test.db', convert_unicode=True) > > db_session = scoped_session(sessionmaker(autocommit=False, > autoflush=False, > > bind=engine)) > > Base = declarative_base() > > Base.query = db_session.query_property() > > > > > > class User(Base): > > __tablename__ = 'users' > > > > id = Column(Integer, primary_key=True) > > name = Column(String(50), unique=True) > > email = Column(String(120), unique=True) > > > > def __init__(self, name=None, email=None): > > self.name = name > > self.email = email > > > > def __repr__(self): > > return '<User %r>' % (self.name) > > > > From a very quick read of the Flask-SQLAlchemy docs, I would have > thought you could just use your flask-based classes in non-Flask-based > apps without any issue. The quickstart guide that you referenced above > illustrates a command-line session using them, so there's no reason > why you couldn't do the same in a worker process. > > Have you already tried it and found that it doesn't work? > > Simon >
Perhaps I've missed the important bit, but my understanding is that there are two ways to do it: 1) Use SQLAlchemy with manual session control ( http://flask.pocoo.org/docs/patterns/sqlalchemy/) 2) Use SQLAlchemy with the Flask-SQLAlchemy extension which does session control for you, but requires you to use it's own declarative base class, db.Model ( http://packages.python.org/Flask-SQLAlchemy/quickstart.html#a-minimal-application ) The problem is that other extensions give you additional features if you use solution #2, but not if you use solution #1, because solution #1 implies that you are going to do everything yourself manually. I'm fine with the way solution #2 handles the sessions and everything else, I just want to be able to use my own declarative base so that the models are more-or-less independent of the app that they are being used in. -- You received this message because you are subscribed to the Google Groups "sqlalchemy" group. To view this discussion on the web visit https://groups.google.com/d/msg/sqlalchemy/-/ZSwms4BOX60J. To post to this group, send email to sqlalchemy@googlegroups.com. To unsubscribe from this group, send email to sqlalchemy+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/sqlalchemy?hl=en.
