我有三个sqlalchemy模型设置,它们都是一对多的关系。User模型包含许多Task模型,而Task模型包含许多Subtask模型。当我执行test_script.py时,我会收到错误消息:sqlalchemy.orm.exc.UnmappedInstanceError: Class 'builtins.NoneType' is not mapped。
我已经阅读并尝试了每个模块上的几种不同的关系。我的目标是能够在User和Task模型中包含其正确的子项列表。最终,我想访问列表项,例如user_x.task[3].subtask[1]。
这是代码, (models,script,error)
models
错误信息
我已经阅读并尝试了每个模块上的几种不同的关系。我的目标是能够在User和Task模型中包含其正确的子项列表。最终,我想访问列表项,例如user_x.task[3].subtask[1]。
这是代码, (models,script,error)
models
class User(Base):
""" User Model for storing user related details """
__tablename__ = 'Users'
id = Column(Integer, primary_key=True, autoincrement=True, nullable=False)
username = Column(String(255), nullable=False)
password_hash = Column(String(128), nullable=False)
email = Column(String(255), nullable=False, unique=True)
created_date = Column(DateTime, default=datetime.utcnow)
tasks = relationship(Task, backref=backref("Users", uselist=False))
def __init__(self, username: str, password_hash: str, email: str):
self.username = username
self.password_hash = password_hash
self.email = email
class Task(Base):
""" Task Model for storing task related details """
__tablename__ = 'Tasks'
id = Column(Integer, primary_key=True, autoincrement=True, nullable=False)
title = Column(String(255), nullable=False)
folder_name = Column(String(255), nullable=True)
due_date = Column(DateTime, nullable=True)
starred = Column(Boolean, default=False)
completed = Column(Boolean, default=False)
note = Column(String, nullable=True)
created_date = Column(DateTime, default=datetime.utcnow)
user_id = Column(Integer, ForeignKey('Users.id'))
subtasks = relationship(Subtask, backref=backref("Tasks", uselist=False))
def __init__(self, title: str, **kwargs):
self.title = title
self.folder_name = kwargs.get('folder_name', None)
self.due_date = kwargs.get('due_date', None)
self.starred = kwargs.get('starred', False)
self.completed = kwargs.get('completed', False)
self.note = kwargs.get('note', None)
class Subtask(Base):
""" Subtask Model for storing subtask related details """
__tablename__ = 'Subtasks'
id = Column(Integer, primary_key=True, nullable=False, autoincrement=True)
title = Column(String(255), nullable=False)
completed = Column(Boolean, default=False)
task_id = Column(Integer, ForeignKey('Tasks.id'))
def __init__(self, title: str, **kwargs):
self.title = title
self.completed = kwargs.get('completed', False)
test_script.py
session1 = create_session()
user1 = User(
username="Stephen",
password_hash="p-hash",
email="stephen@gmail.com"
).tasks.append(
Task(
title='Delete Me',
folder_name='Folder 1'
).subtasks.append(
Subtask(
title='Delete Me 2'
)
)
)
session1.add(user1)
session1.commit()
session1.close()
错误信息
/Users/StephenCollins/Respositories/pycharm_workspace/Personal/BusyAPI_v1/venv/bin/python /Users/StephenCollins/Respositories/pycharm_workspace/Personal/BusyAPI_v1/tests/test_script.py
Traceback (most recent call last):
File "/Users/StephenCollins/Respositories/pycharm_workspace/Personal/BusyAPI_v1/venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 1943, in add
state = attributes.instance_state(instance)
AttributeError: 'NoneType' object has no attribute '_sa_instance_state'
During handling of the above exception, another exception occurred:
Traceback (most recent call last):
File "/Users/StephenCollins/Respositories/pycharm_workspace/Personal/BusyAPI_v1/tests/test_script.py", line 24, in <module>
session1.add(user1)
File "/Users/StephenCollins/Respositories/pycharm_workspace/Personal/BusyAPI_v1/venv/lib/python3.7/site-packages/sqlalchemy/orm/session.py", line 1945, in add
raise exc.UnmappedInstanceError(instance)
sqlalchemy.orm.exc.UnmappedInstanceError: Class 'builtins.NoneType' is not mapped
希望我理解的接近,但如果完全错误,请告诉我。在之前的实习中我使用过Hibernate,但我是自学Python、SQLAlchemy和MySQL的(自学是最好的学习方式)。