SQLAlchemy: AttributeError: 'unicode' object has no attribute '_sa_instance_state'

Question

I've seen other questions with a similar error though their fixes did not solve my issue. Notice that I'm using Flask-SQLAlchemy.

Here is my models file:

class subjects(db.Model):

    id = db.Column(db.Integer, primary_key=True)
    subject = db.Column(db.String(100))

class questions(db.Model):

    id = db.Column(db.Integer, primary_key=True)
    accountID = db.Column(db.Integer, db.ForeignKey('accounts.id'))
    subjectID = db.Column(db.Integer, db.ForeignKey('subjects.id'))
    subject = db.relationship('subjects')
    topic = db.Column(db.String(150), nullable=True)

As you may see, I want questions.subject to refer to subjects.subject. I try to form a query:

topicList = db.session.query(questions.topic.distinct()).filter_by(subject=subjectID, accountID=accountID)

I receive an error stating AttributeError: 'unicode' object has no attribute '_sa_instance_state'

What does this error mean and how to I fix my code to prevent this error? Thanks.

dirn · Accepted Answer · 2015-08-08 14:36:24Z

2

You are filtering by subject, but providing a string instead of an object. You either need to use an object

subject = db.session.query(subjects).get(subjectID)
topicList = db.session.query(questions.topic.distinct()).filter_by(subject=subject, accountID=accountID)

or you need to query by subjectID

topicList = db.session.query(questions.topic.distinct()).filter_by(subjectID=subjectID, accountID=accountID)

In either case, you appear to be using subjectID as a string when it should be an integer. I'm not sure how it's getting its initial value, but you'll want to address that there.

answered Aug 8, 2015 at 14:36

dirn

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