如何摆脱sqlalchemy.exc.NoReferencedTableError？

Question

这里有一些与问题相关的代码：

db_session.py

import sqlalchemy as sa
import sqlalchemy.orm as orm
import sqlalchemy.ext.declarative as dec

SqlAlchemyBase = dec.declarative_base()

__Session = None


def create_session():
    global __Session
    global_init()
    return __Session()


def global_init():
    global __Session

    if __Session:
        return

    conn_str = f'sqlite:///sqlite.db'

    engine = sa.create_engine(conn_str, echo=True, future=True)
    __Session = orm.sessionmaker(bind=engine)

    SqlAlchemyBase.metadata.create_all(engine)

User.py（错误来自 User.department_id 列）

import sqlalchemy
from db_session import SqlAlchemyBase


class User(SqlAlchemyBase):
    __tablename__ = 'users'

    id = sqlalchemy.Column(sqlalchemy.Integer,
                           primary_key=True, autoincrement=True)
    department_id = sqlalchemy.Column(sqlalchemy.Integer, 
                                      sqlalchemy.ForeignKey('departments.id'), nullable=True)

Departments.py

import sqlalchemy
from db_session import SqlAlchemyBase


class Departments(SqlAlchemyBase):
    __tablename__ = 'departments'

    id = sqlalchemy.Column(sqlalchemy.Integer, 
                           primary_key=True, autoincrement=True)
    chief = sqlalchemy.Column(sqlalchemy.Integer, sqlalchemy.ForeignKey("users.id"))
    members = sqlalchemy.orm.relationship("User", foreign_keys="User.department_id")

每当我尝试访问 'users' table 时就会出现错误。这是错误文本：

sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'users.department_id' could not find table 'departments' with which to generate a foreign key to target column 'id'

我用数据库管理软件查看了sqlite.db文件，确实有'departments'table。我打印了

的输出

SqlAlchemyBase.metadata.tables.keys()

'departments' table 也在那里，甚至还有正确的名字。我尝试向 'departments' table 添加一些内容，但这也无济于事。所有 table 的名称都明确设置为 tablename 属性，因此 sqlalchemy 的自动 table 命名不是问题。我该如何摆脱这个错误？

Answer 1

感谢@snakecharmerb 提供解决方案！

事实证明，我必须在任何地方导入部门 class 我使用 sqlalchemy 的用户模型来查找所有表。

如何摆脱sqlalchemy.exc.NoReferencedTableError？

How to get rid of sqlalchemy.exc.NoReferencedTableError?

python

sqlite

sqlalchemy