Flask SqlAlchemy : TypeError: 'Class' object is not iterable
I fail to understand why such an error appears. What is the right way of adding a mapped object ?
Notice that when you configure you wallet relationship you use lazy="dynamic" option. This way you are setting up a dynamic relationship. As it is designed to be used with large collections it doesn't really makes much sense to use it with one-to-one relationship.
At the same time it alters the way you can assign to your scalar relationship, i.e. you cannot assing your single object directly:
self.wallet = wallet
but you must use an iterable
self.wallet = [wallet]
So you have two solutions here: either assign collection of one element as shown above or better yet stop using dynamic collections for this relationship.
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Yace
Updated on October 20, 2022Comments
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Yace over 1 year
I'm following the Flask-SQLAlchemy tutorial. I have Flask 0.9, sqlalchemy 0.7.8 and flask-sqlalchemy 0.16 on python 2.6. (and I work with eclipse)
(The tuto is here : http://packages.python.org/Flask-SQLAlchemy/models.html)
I have 2 classes : a man and a wallet. There is a 1-1 relationship. (Each man has his own wallet)
class Man(db.Model): sid = db.Column(db.Integer, primary_key=True) name = db.Column(db.String(100), unique=False) wallet = db.relationship('Wallet', backref='man', lazy='dynamic', uselist=False) def __init__(self, wallet): self.wallet = wallet class Wallet(db.Model): sid = db.Column(db.Integer, primary_key=True) account = db.Column(db.Integer) manId = db.Column(db.Integer, db.ForeignKey('man.sid')) def __init__(self, account): self.account = account
In my "main" module, I create my database :
app = Flask(__name__) app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:PATH' db = SQLAlchemy(app)
In this very same module, I try to attach a Wallet to a Man :
if __name__ == "__main__": db.create_all() w1 = Wallet(132) w2 = Wallet(18) db.session.add(w1) db.session.add(w2) db.session.commit() man1 = Man(w1) db.session.add(man1) db.session.commit()
But I get this error :
TypeError: 'Wallet' object is not iterable
I fail to understand why such an error appears. What is the right way of adding a mapped object ?
PS : I've been on the SQLAlchemy tutorial and I believe that they would declare things differently :
class Man(db.Model): sid = db.Column(db.Integer, primary_key=True) name = db.Column(db.String(100), unique=False) wallet = db.relationship('Wallet', backref='man', lazy='dynamic', uselist=False) manId = db.Column(db.Integer, db.ForeignKey('man.sid')) def __init__(self, wallet): self.wallet = wallet class Wallet(db.Model): sid = db.Column(db.Integer, primary_key=True) account = db.Column(db.Integer) def __init__(self, account): self.account = account
Which tutorial should I trust ?
Thank you very much !
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zzzeek over 11 yearsthis is basically the right answer. it's nonsensical to use "uselist=False" with "lazy='dynamic'", and I think the 'dynamic' flag here is going to trump the "uselist". Really it shouldn't be allowed at all, will see if I can add that.
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zzzeek over 11 yearsI've updated the docs at docs.sqlalchemy.org/en/rel_0_7/orm/… and there is also a warning in 0.7.9 and an exception raise in 0.8.