Impossible de supprimer une instance de la base de données à l'aide de SQLAlchemy

Question

Je ne peux pas supprimer une instance de la base de données à l'aide de SQLAlchemy.

Voici le code:

from sqlalchemy.orm import sessionmaker, scoped_session 
from zope.sqlalchemy import ZopeTransactionExtension 
from sqlalchemy import create_engine 
from sqlalchemy import MetaData 
from sqlalchemy.ext.declarative import declarative_base 
from pyspatialite import dbapi2 as sqlite 
import transaction 

maker = sessionmaker(autoflush=True, autocommit=False, extension=ZopeTransactionExtension()) 
DBSession = scoped_session(maker) 
metadata = MetaData() 
Base = declarative_base(metadata=metadata) 

filename="/net/my_db.db" 
dburi = 'sqlite:///{0}'.format(filename) 
engine = create_engine(dburi, module=sqlite, echo=False, encoding="utf8") 
metadata.bind = engine 
DBSession.configure(bind=engine) 

my_table = metadata.tables['table_name'] 
name_col = my_table.columns['col_name'] 
my_instance = DBSession.query(my_table).filter(name_col == "toto").first() 

DBSession.delete(my_instance) 

J'ai l'erreur suivante:

UnmappedInstanceError: Class 'sqlalchemy.util._collections.KeyedTuple' is not mapped

Answer 1

J'ai trouvé une réponse qui fonctionne:

my_table = metadata.tables['table_name'] 
name_col = my_table.columns['col_name'] 
id_col = my_table.columns['id'] 
old_id, = DBSession.query(id_col).filter(name_col == "toto").first() 
my_instance = DBSession.query(ClassMap).get(old_id) 

DBSession.delete(my_instance) 

transaction.commit()