ponyorm01.py

from pony import orm

db = orm.Database()
orm.set_sql_debug(True)


class Author(db.Entity):
    name = orm.PrimaryKey(str)
    books = orm.Set('Book')


class Book(db.Entity):
    name = orm.PrimaryKey(str)
    authors = orm.Set(Author)


db.bind(
    provider='sqlite',
    filename=':memory:')
db.generate_mapping(create_tables=True)


@orm.db_session
def init():
    a1 = Author(name='Umberto Eco')
    b1 = Book(name='Il nome della rosa', authors=[a1])
    b1 = Book(name='Il pendolo di Foucault', authors=[a1])

init()