SQLAlchemy DeclarativeMeta example

gistfile1.py

import sqlalchemy
import sqlalchemy.orm
import sqlalchemy.ext.declarative

class BaseClsMeta(sqlalchemy.ext.declarative.DeclarativeMeta):
    def __init__(cls, classname, bases, dict_):
        if getattr(cls, '__dupa__', False):
            for i in range(10):
                fname = 'fid%d' % i
                dict_[fname] = sqlalchemy.Column(fname, sqlalchemy.types.Integer())
                setattr(cls, fname, dict_[fname])
        super(BaseClsMeta, cls).__init__(classname, bases, dict_)


Base = sqlalchemy.ext.declarative.declarative_base(metaclass=BaseClsMeta, mapper=sqlalchemy.orm.mapper)


class Foo(Base):
    __tablename__ = 'foo'
    __dupa__ = True
    id = sqlalchemy.Column('id', sqlalchemy.types.Integer(), primary_key=True)

class Bar(Base):
    __tablename__ = 'bar'
    __dupa__ = False
    id = sqlalchemy.Column('id', sqlalchemy.types.Integer(), primary_key=True)

session = sqlalchemy.orm.scoped_session(sqlalchemy.orm.sessionmaker())
engine = sqlalchemy.create_engine('sqlite:///:memory:', echo =  True)
Base.metadata.create_all(engine)