[Sqlalchemy-tickets] Issue #3858: object has no attribute '_sa_instance_state' (zzzeek/sqlalchemy)

[Mehdi G. <iss...@bi...>]

New issue 3858: object has no attribute '_sa_instance_state'
https://bitbucket.org/zzzeek/sqlalchemy/issues/3858/object-has-no-attribute-_sa_instance_state

Mehdi GMIRA:

Hey,

I don't know if this a bug or something that I should expect this behaviour from SA, but I still find it very weird. Here is the test case:

```python
from sqlalchemy import Column, DateTime, String, Integer, ForeignKey, func, Table, create_engine
from sqlalchemy.orm import relationship, backref, sessionmaker, joinedload, contains_eager
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()
engine = create_engine('sqlite://', echo=False)


class Student(Base):
    __tablename__ = 'student'
    id = Column(Integer, primary_key=True)
    name = Column(String)


Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)
Session = sessionmaker(engine)
session = Session()


session.add(Student(name='foo'))

session.commit()


class Myclass(object):
    column = Student.name

    def test(self):
        print session.query(Student.id, Student.name).filter(self.__class__.column == 'foo').all()  # does not raise
        print session.query(Student.id, Student.name).filter(self.column == 'foo').all()  # raises error


my_class = Myclass()

my_class.test()
```

The error that is raised is: 

```python
AttributeError: 'Myclass' object has no attribute '_sa_instance_state'
```