pony orm在创建数据库之前定义实体子类 我正在创建一个包含bot类的库。我希望它能够在小马ORM的帮助下将消息日志和其他一些信息存储在SQL数据库中。想法是让机器人接受...

Question

from pony import orm

class Message(orm.Entity): 
  text = orm.Required(unicode)

class Database(orm.Database):
  def __init__(self, path):
    # super(..).__init__(..)
    # bind Message to self

class Bot(object):
  def __init__(self, path):
    self.database = Database(path)

现在，如果我可以从数据库继承。

任何想法？也许我可以用Sqlalchemy等另一个ORM来实现这一目标？

您可以尝试以下模式：

from pony import orm


def entities_for_db(db: orm.Database):
    """
    Creates set of entities connected to a specified database.
    :param db: database to which entities should be connected.
    :return: class with database entities.
    """

    class Entities:
        class Language(db.Entity):
            name = orm.Required(str, max_len=128)
            symbol = orm.Required(str, max_len=32)

            @classmethod
            def get_by_symbol(cls, symbol):
                return cls.select(lambda l: l.symbol == symbol).first()

            @classmethod
            def get_or_create(cls, symbol, name):
                return cls.select(lambda l: l.symbol == symbol and l.name == name).first() \
                    or cls(symbol=symbol, name=name)

            def to_dict(self):
                return dict(name=self.name, symbol=self.symbol)

    return Entities


# First sequence run for 2 different databases
db1 = orm.Database(provider='sqlite', filename="test1.sqlite", create_db=True)
db2 = orm.Database(provider='sqlite', filename="test2.sqlite", create_db=True)

db1_entities = entities_for_db(db1)
db2_entities = entities_for_db(db2)

db1.generate_mapping(create_tables=True)
db2.generate_mapping(create_tables=True)

with orm.db_session():
    result1 = db1_entities.Language.get_or_create("en", "English")
    result2 = db2_entities.Language.get_or_create("pl", "Polish")

# Disconnect to let the sequence be run once again
db1.disconnect()
db2.disconnect()

# Second sequence run for the same databases
db1 = orm.Database(provider='sqlite', filename="test1.sqlite", create_db=True)
db2 = orm.Database(provider='sqlite', filename="test2.sqlite", create_db=True)

db1_entities = entities_for_db(db1)
db2_entities = entities_for_db(db2)

db1.generate_mapping(create_tables=True)
db2.generate_mapping(create_tables=True)

with orm.db_session():
    db1_entities.Language.get_or_create("de", "German")
    db2_entities.Language.get_or_create("fr", "French")