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Asked:2024-09-09 04:06:01 +0000 UTC2024-09-09 04:06:01 +0000 UTC

SQLAlchemy 与单独文件中模型的关系

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如果每个模型都在单独的文件中，谁能告诉我如何使用 SQLAlchemy 关系？例子：

# ./models/user.py
class UserModel(Base):
    __tablename__ = 'users'
    id: Mapped[int] = mapped_column(primary_key=True)
    characters: Mapped[list['CharacterModel']] = relationship(back_populates='user')

# ./models/character.py
class CharacterModel(Base):
    __tablename__ = 'characters'
    id: Mapped[int] = mapped_column(primary_key=True)
    user_id: Mapped[int] = mapped_column(ForeignKey('users.id', ondelete='CASCADE'))
    characters: Mapped['UserModel'] = relationship(back_populates='characters')

# ./models/__init__.py
from . import user, character

创建用户时出错：

sqlalchemy.exc.InvalidRequestError: When initializing mapper Mapper[UserModel(users)], expression 'CharacterModel' failed to locate a name ('CharacterModel'). If this is a class name, consider adding this relationship() to the <class 'python.database.models.user.UserModel'> class after both dependent classes have been defined.

我在任何地方都找不到信息，并且在使用模型的示例中它总是在一个文件中。如果有任何信息，我将不胜感激。

python

1 个回答

  1. Best Answer

    我找到了一个解决方案，可能是唯一正确的解决方案。一切都与上面的代码相同，但在最后添加了带注释的导入# noqa: E402

    # ./models/user.py
class UserModel(Base):
    __tablename__ = 'users'
    id: Mapped[int] = mapped_column(primary_key=True)
    characters: Mapped[list['CharacterModel']] = relationship(back_populates='user')

from .character import CharacterModel # noqa: E402


# ./models/character.py
class CharacterModel(Base):
    __tablename__ = 'characters'
    id: Mapped[int] = mapped_column(primary_key=True)
    user_id: Mapped[int] = mapped_column(ForeignKey('users.id', ondelete='CASCADE'))
    characters: Mapped['UserModel'] = relationship(back_populates='characters')

from .user import UserModel # noqa: E402


# ./models/__init__.py
from . import user, character
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