On Feb 8, 2011, at 3:52 PM, farcat wrote:
> Hi everyone,
>
> I am new to sqlalchemy and figuring out whether it is right for my
> project. What I am looking for is the ability to change classes and
> tables on the flight, with as much freedom as possible, potentially
> having metaclasses figuring out the difference between versions and
> updating the database accordingly. Additionally I would like to import
> databases and automatically generate class definitions. Some code I
> tried:
>
> <code>
> from sqlalchemy import *
> from sqlalchemy.ext.declarative import declarative_base
> from sqlalchemy.orm import relation, sessionmaker
>
> Base = declarative_base()
>
> def Init(self, title=None, year=None):
> self.title = title
> self.year = year
> def Repr(self):
> return "Movie(%r, %r, %r)" % (self.title, self.year,
> self.director)
>
> Movie = type("Movie", (Base,),{'__tablename__': "movies",
> "id":Column(Integer, primary_key=True),
> "title": Column(String(255), nullable=False),
> "year": Column(Integer),
> "directed_by": Column(Integer,
> ForeignKey('directors.id')),
> "director": relation("Director", backref='movies',
> lazy=False)})
> setattr(Movie, "__init__", classmethod(Init))
> setattr(Movie, "__repr__", classmethod(Repr))
>
>
> class Director(Base):
> __tablename__ = 'directors'
>
> id = Column(Integer, primary_key=True)
> name = Column(String(50), nullable=False, unique=True)
>
> def __init__(self, name=None):
> self.name = name
>
> def __repr__(self):
> return "Director(%r)" % (self.name)
>
> engine = create_engine('sqlite:///meta.db', echo=True)
> Base.metadata.create_all(engine)
>
> if __name__ == "__main__":
> Session = sessionmaker(bind=engine)
> session = Session()
>
> m1 = Movie("Star Trek", 2009)
> m1.director = Director("JJ Abrams")
>
> d2 = Director("George Lucas")
> d2.movies = [Movie("Star Wars", 1977), Movie("THX 1138", 1971)]
>
> try:
> session.add(m1)
> session.add(d2)
> session.commit()
> except:
> session.rollback()
>
> alldata = session.query(Movie).all()
> for somedata in alldata:
> print somedata
>
> <\code>
>
> with as error:
>
>
> 2011-02-08 21:50:47,553 INFO sqlalchemy.engine.base.Engine.0x...ef0L
> PRAGMA table_info("directors")
> 2011-02-08 21:50:47,553 INFO sqlalchemy.engine.base.Engine.0x...ef0L
> ()
> Traceback (most recent call last):
> File "D:\Documents\Code\NetBeans\test\alchemy\src\alchemy.py", line
> 49, in <module>
> m1.director = Director("JJ Abrams")
> File "C:\Python27\lib\site-packages\sqlalchemy\orm\attributes.py",
> line 158, in __set__
> 2011-02-08 21:50:47,555 INFO sqlalchemy.engine.base.Engine.0x...ef0L
> PRAGMA table_info("movies")
> 2011-02-08 21:50:47,555 INFO sqlalchemy.engine.base.Engine.0x...ef0L
> ()
> self.impl.set(instance_state(instance),
> AttributeError: 'Movie' object has no attribute '_sa_instance_state'
>
> Can anyone shed some light or explain the error message?
your __init__ monkeypatch is interfering with SQLA's wrapping of this method.
Try
Movie = type("Movie", (Base,),{'__tablename__': "movies",
"__init__":Init,
"id":Column(Integer, primary_key=True),
"title": Column(String(255), nullable=False),
"year": Column(Integer),
"directed_by": Column(Integer,ForeignKey('directors.id')),
"director": relation("Director",
backref='movies',lazy=False)})
instead.
>
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