Python flask_sqlalchemy: AttributeError: 'Table' object 没有属性 ' added_by'

Question

这是我的 model class，它定义了所有数据库对象。 （我已经从另一个 package 导入了 db object，这是 sqlAlchemy() 的一个实例）

from datetime import datetime
from TasMar import  db, login_manager
from flask import  current_app
from flask_login import UserMixin

@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))

class User(db.Model, UserMixin):
    __tablename__ = 'tm_user'
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(20),unique=True, nullable=False)
    email = db.Column(db.String(120),unique=True, nullable=False)
    image_file = db.Column(db.String(20), nullable=False, default='default.jpg')
    password=  db.Column(db.String(120), nullable=False)

    #foreign keys accessing this table's primary keys
    added = db.relationship('Tasks', lazy=True, foreign_keys='tm_task.added_by')
    assigned = db.relationship('Tasks', lazy=True, foreign_keys='tm_task.assigned_to')

    def __repr__(self):
            return "User('{}','{}','{}')".format(self.username,self.email,self.image_file)


class Tasks(db.Model):
    __tablename__ = 'tm_task'
    task_id = db.Column(db.Integer, primary_key=True)
    parent_id = db.Column(db.Integer, db.ForeignKey('tm_task.task_id'),nullable=True)
    descr = db.Column(db.String(500), nullable=False)
    added_on = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    added_by = db.Column(db.Integer, db.ForeignKey('tm_user.id'),nullable=False)
    assigned_to = db.Column(db.Integer, db.ForeignKey('tm_user.id'),nullable=False)
    last_updated = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    remark = db.Column(db.Text)


    parent = db.relationship('Tasks', remote_side=[task_id]) #self referential
    status = db.Column(db.Integer, db.ForeignKey('tm_status.id'),nullable=False)
    type = db.Column(db.Integer, db.ForeignKey('tm_type.id'),nullable=False)
    urgency = db.Column(db.Integer, db.ForeignKey('tm_urgency.id'),nullable=False)

    def __repr__(self):
            return "Tasks('{}','{}','{}','{}')".format(self.descr,self.added_on,self.added_by,self.assigned_to)

class tm_status(db.Model):
    __tablename__ = 'tm_status'
    id = db.Column(db.Integer, primary_key=True)
    status = db.Column(db.String(20),unique=True,nullable=False)
    status_f = db.relationship('Tasks', lazy=True, foreign_keys='tm_task.status')

    def __repr__(self):
            return "tm_status('{}')".format(self.status)

class tm_type(db.Model):
    __tablename__ = 'tm_type'
    id = db.Column(db.Integer, primary_key=True)
    type = db.Column(db.String(20),unique=True,nullable=False)
    type_f = db.relationship('Tasks', lazy=True, foreign_keys='tm_task.type')

    def __repr__(self):
            return "tm_type('{}')".format(self.type)

class tm_urgency(db.Model):
    __tablename__ = 'tm_urgency'
    id = db.Column(db.Integer, primary_key=True)
    urgency = db.Column(db.String(20),unique=True,nullable=False)
    urgency_f = db.relationship('Tasks', lazy=True, foreign_keys='tm_task.urgency')

    def __repr__(self):
            return "tm_urgency('{}')".format(self.urgency)

我使用另一个 class 创建这些对象并查询数据如下

from TasMar import db,create_app
from TasMar.models import User,Tasks,tm_status, tm_urgency,tm_type
app=create_app()
app.app_context().push()
#db.create_all()   #<<works perfectly but not below !
user = User.query.filter_by(email='dummy@email.com').first()
print(user)

create_all() 工作正常，它创建具有正确关系的所有模式对象，但是查询数据会出错。 （即运行上面的代码给出如下错误） AttributeError: 'Table' object has no attribute ' added_by'为什么我会收到这个错误？

Traceback (most recent call last):
  File "F:\My Documents\Official\work\EclipseWorkspace\TaMar\setup_db.py", line 7, in <module>
    user = User.query.filter_by(email='dummy@email.com').first()
  File "F:\Installations\Anaconda\lib\site-packages\flask_sqlalchemy\__init__.py", line 517, in __get__
    mapper = orm.class_mapper(type)
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\orm\base.py", line 421, in class_mapper
    mapper = _inspect_mapped_class(class_, configure=configure)
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\orm\base.py", line 400, in _inspect_mapped_class
    mapper._configure_all()
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\orm\mapper.py", line 1268, in _configure_all
    configure_mappers()
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\orm\mapper.py", line 3013, in configure_mappers
    mapper._post_configure_properties()
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\orm\mapper.py", line 1811, in _post_configure_properties
    prop.init()
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\orm\interfaces.py", line 184, in init
    self.do_init()
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\orm\relationships.py", line 1655, in do_init
    self._process_dependent_arguments()
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\orm\relationships.py", line 1680, in _process_dependent_arguments
    setattr(self, attr, attr_value())
  File "F:\Installations\Anaconda\lib\site-packages\sqlalchemy\ext\declarative\clsregistry.py", line 281, in __call__
    x = eval(self.arg, globals(), self._dict)
  File "<string>", line 1, in <module>
AttributeError: 'Table' object has no attribute 'added_by'

Answer 1

我设法解决了这个问题。 显然我混淆了 class 名称和表名，这是工作更新代码，查看“added_by”列的更新外键数据。

from datetime import datetime
from TasMar import  db, login_manager
from flask import  current_app
from flask_login import UserMixin
from itsdangerous import TimedJSONWebSignatureSerializer as Serializer

@login_manager.user_loader
def load_user(user_id):
    return User.query.get(int(user_id))

class User(db.Model, UserMixin):
    __tablename__ = 'tm_user'
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String(20),unique=True, nullable=False)
    email = db.Column(db.String(120),unique=True, nullable=False)
    image_file = db.Column(db.String(20), nullable=False, default='default.jpg')
    password=  db.Column(db.String(120), nullable=False)

    #foreign keys accessing this table's primary keys
    added_by = db.relationship('Tasks',backref='addedby', lazy=True, foreign_keys='Tasks.added_by')
    assigned_to = db.relationship('Tasks',backref='user', lazy=True, foreign_keys='Tasks.assigned_to')

    def __repr__(self):
            return "User('{}','{}','{}')".format(self.username,self.email,self.image_file)



class Tasks(db.Model):
    __tablename__ = 'tm_task'
    task_id = db.Column(db.Integer, primary_key=True)
    parent_id = db.Column(db.Integer, db.ForeignKey('tm_task.task_id'),nullable=True)
    descr = db.Column(db.String(500), nullable=False)
    added_on = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    assigned_to = db.Column(db.Integer, db.ForeignKey('tm_user.id'),nullable=False)
    added_by = db.Column(db.Integer, db.ForeignKey('tm_user.id'),nullable=False)
    target_date = db.Column(db.DateTime,nullable=True,default=None)
    last_updated = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
    remark = db.Column(db.Text)
    #foreign keys accessing this table's primary keys
    parent = db.relationship('Tasks', remote_side=[task_id]) #self referential
    status = db.Column(db.Integer, db.ForeignKey('tm_status.id'),nullable=False)
    type = db.Column(db.Integer, db.ForeignKey('tm_type.id'),nullable=False)
    urgency = db.Column(db.Integer, db.ForeignKey('tm_urgency.id'),nullable=False)

    def __repr__(self):
            return "Tasks('{}','{}','{}','{}')".format(self.descr,self.added_on,self.added_by,self.assigned_to)

class tm_status(db.Model):
    __tablename__ = 'tm_status'
    id = db.Column(db.Integer, primary_key=True)
    status = db.Column(db.String(20),unique=True,nullable=False)
    status_f = db.relationship('Tasks',backref='status_f', lazy=True, foreign_keys='Tasks.status')

    def __repr__(self):
            return "tm_status('{}')".format(self.status)

class tm_type(db.Model):
    __tablename__ = 'tm_type'
    id = db.Column(db.Integer, primary_key=True)
    type = db.Column(db.String(20),unique=True,nullable=False)
    type_f = db.relationship('Tasks',backref='type_f', lazy=True, foreign_keys='Tasks.type')

    def __repr__(self):
            return "tm_type('{}')".format(self.type)

class tm_urgency(db.Model):
    __tablename__ = 'tm_urgency'
    id = db.Column(db.Integer, primary_key=True)
    urgency = db.Column(db.String(20),unique=True,nullable=False)
    urgency_f = db.relationship('Tasks', backref='urgency_f', lazy=True, foreign_keys='Tasks.urgency')

    def __repr__(self):
            return "tm_urgency('{}')".format(self.urgency)