from yff import db, login_manager, app
from flask_login import UserMixin
import datetime
import jwt
#login_manager.user_loader
def load_user(user_id):
return User.query.get(int(user_id))
class User(db.Model, UserMixin):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(20), unique=True, nullable=False)
password = db.Column(db.String(120), unique=False, nullable=False)
email = db.Column(db.String(50), unique=False, nullable=False)
profile_pic = db.Column(db.String(30), unique=False, default="default.jpg")
is_moderator = db.Column(db.Boolean, default=False)
posts = db.relationship('Posts', backref='author', lazy=True)
likes = db.relationship('Likes', backref='user', passive_deletes=True)
comments = db.relationship('Comment', backref='user', passive_deletes=True)
def get_reset_token(self):
encoded = jwt.encode({'user_id':self.id, "exp":datetime.datetime.now() + datetime.timedelta(hours = 0.5)}, app.config['SECRET_KEY'], algorithm='HS256')
return encoded
#staticmethod
def verify_secret_token(token):
try:
decoded = jwt.decode(token, options={"verify_signature": False})
user_id = decoded['user_id']
except:
return None
return User.query.get(user_id)
def __repr__(self):
return f'{self.username}, {self.email}'
class Image(db.Model):
id = db.Column(db.Integer, primary_key=True)
title=db.Column(db.String(120), nullable=False)
date_created = db.Column(db.DateTime, nullable=False, default=datetime.datetime.now(tz=datetime.timezone.utc))
img_location = db.Column(db.String(600), nullable=False)
mimetype = db.Column(db.String(10))
post_name = db.Column(db.String(150),nullable=False, unique=False)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
manga_name = db.Column(db.String(100), unique=False, nullable=False)
class Posts(db.Model):
id = db.Column(db.Integer, primary_key=True)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
post_id = db.Column(db.Integer, db.ForeignKey('image.id', ondelete="CASCADE"), nullable=False)
likes = db.Column(db.Integer, db.ForeignKey('likes.id', ondelete='CASCADE'))
date_created = db.Column(db.DateTime, nullable=False, default=datetime.datetime.now(tz=datetime.timezone.utc))
comments = db.relationship('Comment', backref='Posts', passive_deletes=True)
class Likes(db.Model):
id = db.Column(db.Integer, primary_key=True)
author = db.Column(db.Integer, db.ForeignKey('user.id', ondelete="CASCADE"), nullable=False)
post_id = db.Column(db.Integer, db.ForeignKey('image.id', ondelete="CASCADE"), nullable=False)
liked_post = db.relationship('Posts', backref='post')
class Comment(db.Model): #import it in the __init__ file
id = db.Column(db.Integer, primary_key=True)
text = db.Column(db.String(1000), nullable=False)
date_created = db.Column(db.DateTime, nullable=False, default=datetime.datetime.now(tz=datetime.timezone.utc))
author = db.Column(db.Integer, db.ForeignKey('user.id', ondelete="CASCADE"), nullable=False)
post_id = db.Column(db.Integer, db.ForeignKey('image.id', ondelete="CASCADE"), nullable=False)
The following is the entire error:
sqlalchemy.exc.InvalidRequestError: One or more mappers failed to initialize - can't proceed with initialization of other mappers. Triggering mapper: 'mapped class Posts->posts'. Original exception was: Could not determine join condition between parent/child tables on relationship Posts.comments - there are no foreign keys linking these tables. Ensure that referencing columns are associated with a ForeignKey or ForeignKeyConstraint, or specify a 'primaryjoin' expression.
I am getting this error in the pythonanywhere error log. I tried changing the positions of the backref statement but I that did not help. (I am new to web dev and I still haven't figured out how backref works)
I know how foreign keys work in SQL but I am still not experienced at OOP and SQLAlchemy, so please help me out.
Am trying to create (one to many relationship between three tables) where the Student table is able to extend its id to the (StudentQuestion and Mark)tables respectivley. But i get an error concerning the (Lazy=True) argument from the student table and failing to understand why!!
from datetime import datetime
from ..utils.db import db
class Student(db.Model):
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(255), nullable=True, default='default.jpg')
password = db.Column(db.String(60), nullable=False)
student_qn = db.relationship('StudentQuestion', backref='examinee', lazy='True')
student_mark = db.relationship('Mark', backref='mark')
def __repr__(self):
return f"Student('{self.username}', '{self.email}')"
def save(self):
db.session.add(self)
db.session.commit()
class Mark(db.Model):
id = db.Column(db.Integer, primary_key=True)
percentage_mark = db.Column(db.Integer, nullable=False)
grade = db.Column(db.String(20), nullable=False)
student_id = db.Column(db.Integer, db.ForeignKey('student.id'), nullable=False)
def __repr__(self):
return f"Mark('{self.percentage_mark}','{self.grade}')"
def save(self):
db.session.add(self)
db.session.commit()
class StudentQuestion(db.Model):
id = db.Column(db.String, primary_key=True)
passage = db.Column(db.Text, nullable=False)
passage_question = db.Column(db.Text, nullable=False)
date_qn_attempt = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
answer = db.Column(db.Text, nullable=False)
student_id = db.Column(db.Integer, db.ForeignKey('student.id'), nullable=False)
def __repr__(self):
return f"StudentQuestion('{self.passage}','{self.passage_question}', '{self.date_qn_attempt}','{self.answer}')"
def save(self):
db.session.add(self)
db.session.commit()
The defined relationship requires the parameter lazy to be a boolean. Not a string, as provided in the question.
Change this row:
student_qn = db.relationship('StudentQuestion', backref='examinee', lazy='True')
To:
student_qn = db.relationship('StudentQuestion', backref='examinee', lazy=True)
I can't find a way to get all messages from the user via user.messages and the same via channel.messages. I keep getting an error with foreignkeys. What do I need to change to my relationships to make it work?
I would like to be able to:
user.messages and channel.messages
and as an extra (if at all possible):
message.user.username or message.user.id
my classes:
class User(db.Model, UserMixin):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(20), unique=True, nullable=False)
password = db.Column(db.String, nullable=False)
email = db.Column(db.String, unique=True, nullable=False)
admin = db.Column(db.Boolean, default=False)
mc_access = db.Column(db.Boolean, default=False)
pass_recov_code = db.Column(db.String, default=None)
all_messages = db.relationship("Message",
backref=db.backref("Message"),
primaryjoin="foreign(User.id) == remote(Message.sender_id)",
foreign_keys="[User.id, User.username]",
cascade="all, delete"
)
class Channel(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(20), unique=True, nullable=False)
uses_password = db.Column(db.Boolean, default=False)
password = db.Column(db.String)
online_users = db.Column(db.String, default=json.dumps([]))
messages = db.relationship("Message", cascade="all, delete", foreign_keys="[Channel.id]", backref=db.backref("channel"))
maker_id = db.Column(db.Integer, nullable=False)
class Message(db.Model):
id = db.Column(db.Integer, primary_key=True)
sender_id = db.Column(db.Integer, db.ForeignKey("user.id"), nullable=False)
sender_username = db.Column(db.String, db.ForeignKey("user.username"), nullable=False)
channel_id = db.Column(db.Integer, db.ForeignKey("channel.id"), nullable=False)
message = db.Column(db.String, default="", nullable=False)
send_on = db.Column(db.String, nullable=False)
edited = db.Column(db.Boolean, default=False)
Simply do the following:
class User(db.Model, UserMixin):
...
messages = db.relationship("Message", back_populates="user")
class Channel(db.Model):
...
messages = db.relationship("Message", back_populates="channel")
class Message(db.Model):
...
sender_id = db.Column(db.Integer, db.ForeignKey("user.id"), nullable=False)
channel_id = db.Column(db.Integer, db.ForeignKey("channel.id"), nullable=False)
user = db.relationship("User", back_populates="messages")
channel = db.relationship("Channel", back_populates="messages")
This way you can use user.messages, channel.messages, message.user.username and message.user.id.
Note: you can also use backref instead of back_populates, but I recommend using back_populates as it is more explicit.
I'm trying to create to blog but I'm having issues creating database using sqlite as my database engine in which I created classes to define each table schema using an ORM with flask-sqlalchemy and also another thing I noticed was it created an empty blog.db file. I cant solve the issue im having right now. As of now this is my resort for help before using Firebase.
models.py
from blogent import db
class User(db.Model):
id = db.Column(db.Integer, primary_key=True)
first_name = db.Column(db.String(50), nullable=False)
last_name = db.Column(db.String(50), nullable=False)
email = db.column(db.String(50), unique=True, nullable=False)
image = db.Column(db.String(20), nullable=False, default='default.jpg')
password = db.Column(db.String(50), nullable=False)
post = db.relationship('Post', backref='author', lazy=True)
created_at = db.Column(db.DateTime, default=datetime.utcnow())
updated_at = db.Column(db.DateTime, default=datetime.utcnow())
def __repr__(self):
return f"User('{self.email}', '{self.image}', '{self.created_at}')"
class Post(db.Model):
id = db.Column(db.Integer, primary_key=True)
post_name = db.Column(db.String(30), nullable=False)
post_title = db.Column(db.Text, nullable=False)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
comments = db.relationship('Comments', backref='posts', lazy=True)
user = db.relationship('User', backref='users', lazy=True)
created_at = db.Column(db.DateTime, default=datetime.utcnow())
updated_at = db.Column(db.DateTime, default=datetime.utcnow())
def __repr__(self):
return f"Post('{self.post_name}', '{self.post_title}', '{self.created_at}')"
class Comments(db.Model):
id = db.Column(db.Integer, primary_key=True)
post_id = db.Column(db.Integer, db.ForeignKey('post.id'))
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
content = db.Column(db.Text, nullable=False)
created_at = db.Column(db.DateTime, default=datetime.utcnow())
updated_at = db.Column(db.DateTime, default=datetime.utcnow())
def __repr__(self):
return f"Comments('{self.content}', '{self.created_at}')"
init.py
from flask_cors import CORS
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = "sqlite:///blog.db"
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SQLALCHEMY_ECHO'] = True
app.config['SECRET_KEY'] = '48ea69eb3539fbe7e069deee6c74d46d'
db = SQLAlchemy(app)
#app.before_first_request
def create_tables():
db.create_all()
from blogent import routes
I'm sory for this newby question, but I can't figure it out for a couple days and it is driving me nuts.
I'm building a small project in order to learn flask, SqlAlchemy and Postrges.
I have major problems with declaring classes in SqlAlchemy. I have already simplified models by removing all many-to-many relationships. However, now I have new problems even with one-to many relationships, although I think I have tried all the possible options. Maybe there's a typo that I keep on overlooking, or I don't grasp something fundamental. Please let me know...
So, I have classes declared as follows in my models.py:
#login_manager.user_loader
def load_user(user_id):
return User.query.get(int(user_id))
class User(db.Model, UserMixin):
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)
password = db.Column(db.String(60), nullable=False)
date_registered = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
role = db.Column(db.Integer, nullable=False)
role_exp_date = db.Column(db.DateTime)
#o2o
personal_datas = db.relationship('PersonalData', uselist=False, backref='user', lazy=True)
persons = db.relationship('Person', uselist=False, backref='user', lazy=True)
#o2m
posts = db.relationship('Post', backref='author', lazy=True)
comments = db.relationship('PostComment', backref='author', lazy=True)
projects_owned = db.relationship('ConstrProject', backref='owner', lazy=True)
attachments = db.relationship('Attachment', backref='author', lazy=True)
def __repr__(self):
return f"{self.username} ({self.email})"
class PersonalData(db.Model):
id = db.Column(db.Integer, primary_key = True)
date_birth = db.Column(db.DateTime)
image_file = db.Column(db.String(20), nullable=False, default='default.jpg')
interests = db.Column(db.Text)
experties = db.Column(db.Text) #Потом сделать отдельную таблицу...
#o2o
user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
#o2m
class Person(db.Model):
id = db.Column(db.Integer, primary_key = True)
first_name = db.Column(db.String(30), nullable=False)
middle_name = db.Column(db.String(40), nullable=False)
last_name = db.Column(db.String(60), nullable=False)
email = db.Column(db.String(120))
license = db.Column(db.String(120))
address = db.Column(db.String(240))
telephone = db.Column(db.String(30))
#o2o
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
#o2m
signers = db.relationship('Signer', backref='person', lazy=True)
def __repr__(self):
return f"{self.last_name.Capitalize} {self.first_name[0].Upper}. {self.middle_name[0].Upper}."
class ConstrProject(db.Model):
__tablename__ = 'constrproject'
id = db.Column(db.Integer, primary_key = True)
name = db.Column(db.String(120), nullable=False, default='New Project')
full_title = db.Column(db.Text, default='New Project')
notes = db.Column(db.Text)
public = db.Column(db.Boolean, default=True) #? check expamples
date_created = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
date_last_edit = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
document_template = db.Column(db.Integer, nullable=False, default=1) #later to m2m
print_settings = db.Column(db.Integer, nullable=False, default=1) #later to m2m
address = db.Column(db.String(240))
#o2m
documents = db.relationship('Document', backref='project', lazy=True)
#m2o
owner_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False) #+ #default = CurrentUser
developer_id = db.Column(db.Integer, db.ForeignKey('company.id'))
main_contractor_id = db.Column(db.Integer, db.ForeignKey('company.id'))
architect_id = db.Column(db.Integer, db.ForeignKey('company.id'))
subcontractor_id = db.Column(db.Integer, db.ForeignKey('company.id'))
other_id = db.Column(db.Integer, db.ForeignKey('company.id'))
developer = db.relationship('Company', foreign_keys=[developer_id], back_populates='constr_projects_developed')
main_contractor = db.relationship('Company', foreign_keys=[main_contractor_id], back_populates='constr_projects_main_contracts')
architect = db.relationship('Company', foreign_keys=[architect_id], back_populates='constr_projects_architect')
subcontractor = db.relationship('Company', foreign_keys=[subcontractor_id], back_populates='constr_projects_subcontracts')
other = db.relationship('Company', foreign_keys=[other_id], back_populates='constr_projects_other')
tech_control_reps_id = db.Column(db.Integer, db.ForeignKey('signer.id'), nullable=False)
main_contractor_reps_id = db.Column(db.Integer, db.ForeignKey('signer.id'), nullable=False)
architect_reps_id = db.Column(db.Integer, db.ForeignKey('signer.id'), nullable=False)
subcontractor_reps_id = db.Column(db.Integer, db.ForeignKey('signer.id'), nullable=False)
other_reps_id = db.Column(db.Integer, db.ForeignKey('signer.id'), nullable=False)
tech_control_reps = db.relationship('Signer', foreign_keys=[tech_control_reps_id], back_populates='tech_control_projects')
main_contractor_reps = db.relationship('Signer', foreign_keys=[main_contractor_reps_id], back_populates='main_contractor_projects')
architect_reps = db.relationship('Signer', foreign_keys=[architect_reps_id], back_populates='architect_projects')
subcontractor_reps = db.relationship('Signer', foreign_keys=[subcontractor_reps_id], back_populates='subcontractor_projects')
other_reps = db.relationship('Signer', foreign_keys=[other_reps_id], back_populates='others_projects')
def __repr__(self):
return f"Site: {self.name}, (id{self.id})"
class Signer(db.Model):
id = db.Column(db.Integer, primary_key = True)
decree = db.Column(db.String(120))
job_title = db.Column(db.String(120))
date_duty_start = db.Column(db.DateTime)
date_duty_end = db.Column(db.DateTime)
#o2m
person_id = db.Column(db.Integer, db.ForeignKey('person.id'), nullable=False)
company_id = db.Column(db.Integer, db.ForeignKey('company.id'), nullable=False)
#m2o
tech_control_projects = db.relationship('ConstrProject', back_populates='tech_control_reps')
main_contractor_projects = db.relationship('ConstrProject', back_populates='main_contractor_reps')
architect_projects = db.relationship('ConstrProject', back_populates='architect_reps')
subcontractor_projects = db.relationship('ConstrProject', back_populates='subcontractor_reps')
others_projects = db.relationship('ConstrProject', back_populates='other_reps')
def __repr__(self):
return f"{self.job_title} as per {self.decree}." #название компании как подтянуть
class Company(db.Model):
id = db.Column(db.Integer, primary_key = True)
name = db.Column(db.String(60))
full_title = db.Column(db.String(240))
tin = db.Column(db.Integer)
kpp = db.Column(db.Integer)
ogrn = db.Column(db.Integer)
email = db.Column(db.String(120))
address = db.Column(db.String(240))
telephone = db.Column(db.String(30))
#o2m
license_number = db.Column(db.String(40), nullable = False)
license_date_issued = db.Column(db.DateTime)
license_category = db.Column(db.String(120), default = '2nd')
license_issued_by = db.Column(db.String(120))
license_issued_by_tin = db.Column(db.Integer)
license_issued_by_kpp = db.Column(db.Integer)
license_issued_by_ogrn = db.Column(db.Integer)
signers = db.relationship('Signer', backref='company', lazy=True)
constr_projects_developed = db.relationship('ConstrProject', back_populates='developer')
constr_projects_main_contracts = db.relationship('ConstrProject', back_populates='main_contractor')
constr_projects_architect = db.relationship('ConstrProject', back_populates='architect')
constr_projects_subcontracts = db.relationship('ConstrProject', back_populates='subcontractor')
constr_projects_other = db.relationship('ConstrProject', back_populates='other')
def __repr__(self):
return f"{self.name}"
class Post(db.Model):
id = db.Column(db.Integer, primary_key = True)
title = db.Column(db.String(100), nullable=False)
date_posted = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
content = db.Column(db.Text, nullable=False)
#o2m
comments = db.relationship('PostComment', backref='Post', lazy=True)
#m2o
user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
def __repr__(self):
return f"Post('{self.title}', '{self.date_posted}')"
class PostComment(db.Model):
id = db.Column(db.Integer, primary_key = True)
date_posted = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
content = db.Column(db.Text, nullable=False)
#m2o
user_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
post_id = db.Column(db.Integer, db.ForeignKey('post.id'), nullable=False)
def __repr__(self):
return f"Comment('{self.id}', '{self.date_posted}')"
class Document(db.Model):
id = db.Column(db.Integer, primary_key = True)
type = db.Column(db.String(60), nullable=False, default='АОСР')
date_last_edit = db.Column(db.DateTime, nullable=False, default=datetime.utcnow)
notes = db.Column(db.Text)
public = db.Column(db.Boolean, default=True)
number = db.Column(db.String(20), nullable=False)
date = db.Column(db.DateTime, default=datetime.utcnow)
job_name = db.Column(db.Text) #? обязательный? на каком этапе делать проверку?
job_place = db.Column(db.String(200))
date_job_start = db.Column(db.DateTime, default=datetime.utcnow)
date_job_end = db.Column(db.DateTime, default=datetime.utcnow)
regulations = db.Column(db.Text)
next_job_allowed = db.Column(db.String(240))
attachments_user_defined = db.Column(db.Text)
#o2m
attachments = db.relationship('Attachment', backref='document', lazy=True)
#m2o
project_id = db.Column(db.Integer, db.ForeignKey('constrproject.id'), nullable=False)
author_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
#m2m
arch_docs = db.Column(db.Text)
building_materials = db.Column(db.Text)
work_drawings = db.Column(db.Text)
def __repr__(self):
return f"АОСР ('{self.number}', '{self.job_name} {self.job_place}', '{self.project}' )"
class Attachment(db.Model):
id = db.Column(db.Integer, primary_key = True)
type_of_document = db.Column(db.String(60), nullable=False, default="QAC")
number = db.Column(db.String(50), nullable=False)
date = db.Column(db.DateTime)
date_valid_start = db.Column(db.DateTime)
date_valid_end = db.Column(db.DateTime)
contents = db.Column(db.Text)
type_of_file = db.Column(db.String(10), nullable=False, default = 'jpg')
image_file = db.Column(db.String(20), nullable=False)
#m2o
author_id = db.Column(db.Integer, db.ForeignKey('user.id'), nullable=False)
document_id = db.Column(db.Integer, db.ForeignKey('document.id'), nullable=False)
def __repr__(self):
if self.text:
return f'{self.text}'
return f'+{self.type_of_document} id{self.id} ({self.type_of_file})'
I cannot understand why, when I try to create an instance of a "Document"
I get errors like this:
sqlalchemy.exc.AmbiguousForeignKeysError: Could not determine join
condition between parent/child tables on relationship
Signer.tech_control_projects - there are multiple foreign key paths
linking the tables. Specify the 'foreign_keys' argument, providing a
list of those columns which should be counted as containing a foreign
key reference to the parent table.
or
sqlalchemy.exc.InvalidRequestError: When initializing mapper
Mapper|ConstrProject|constrproject, expression 'tech_control_reps_id'
failed to locate a name ("name 'tech_control_reps_id' is not
defined"). If this is a class name, consider adding this
relationship() to the class
after both dependent classes have been defined.
I haven't even tried to create these classes. Adding "foreign_keys" doesn't seem to help either. all relationships declared as strings. I tried to use lambda's also without success.
Nevertheless moving the order of class declearations alters the error messages i get...
I cannot find any good examples (resources) of more complicated databases with multiple many-to-many and one-to-many relationships in Each class. Usually examples are very basic and obvious.
So I would really appreciate if you post links to such projects or tutorials.
I wanted to learn some of it myself so I created a working example with one-to-one and multiple one-to-many relationships based on your code (User, Person, Post and Comment classes). I hope it will be a good (simple but not trivial) example for you.
'''SQLAlchemy one-to-one and one-to-many SSCCE'''
import sqlalchemy
import sqlalchemy.ext.declarative
from passlib.hash import pbkdf2_sha256
Base = sqlalchemy.ext.declarative.declarative_base()
class User(Base):
__tablename__ = 'users'
user_id = sqlalchemy.Column(sqlalchemy.Integer, primary_key=True)
username = sqlalchemy.Column(sqlalchemy.String(20), unique=True, nullable=False)
email = sqlalchemy.Column(sqlalchemy.String(120), unique=True, nullable=False)
password = sqlalchemy.Column(sqlalchemy.String(100), nullable=False)
registered = sqlalchemy.Column(
sqlalchemy.DateTime(timezone=True),
nullable=False,
server_default=sqlalchemy.func.now()
)
#o2o
person = sqlalchemy.orm.relationship(
'Person',
uselist=False,
back_populates='user',
lazy='joined'
)
#o2m
posts = sqlalchemy.orm.relationship('Post', back_populates='user')
comments = sqlalchemy.orm.relationship('Comment', back_populates='user')
def __repr__(self):
return f'{self.username} ({self.email})'
class Person(Base):
__tablename__ = 'persons'
person_id = sqlalchemy.Column(
sqlalchemy.Integer,
sqlalchemy.ForeignKey('users.user_id'),
primary_key=True
)
first_name = sqlalchemy.Column(sqlalchemy.String(30), nullable=False)
middle_name = sqlalchemy.Column(sqlalchemy.String(40), nullable=False)
last_name = sqlalchemy.Column(sqlalchemy.String(60), nullable=False)
#o2o
user = sqlalchemy.orm.relationship('User', back_populates='person', lazy='joined')
def __repr__(self):
return (
f'{self.last_name.upper()}'
f' {self.first_name[:1].upper()}.'
f' {self.middle_name[:1].upper()}.'
)
class Post(Base):
__tablename__ = 'posts'
post_id = sqlalchemy.Column(sqlalchemy.Integer, primary_key=True)
title = sqlalchemy.Column(sqlalchemy.String(100), nullable=False)
posted = sqlalchemy.Column(
sqlalchemy.DateTime(timezone=True),
nullable=False,
server_default=sqlalchemy.func.now()
)
content = sqlalchemy.Column(sqlalchemy.Text, nullable=False)
#o2m
comments = sqlalchemy.orm.relationship('Comment', back_populates='post')
#m2o
user_id = sqlalchemy.Column(
sqlalchemy.Integer,
sqlalchemy.ForeignKey('users.user_id'),
nullable=False
)
user = sqlalchemy.orm.relationship('User', uselist=False, back_populates='posts', lazy='joined')
def __repr__(self):
return f'Post({self.title!r}, {self.posted!r})'
class Comment(Base):
__tablename__ = 'comments'
comment_id = sqlalchemy.Column(sqlalchemy.Integer, primary_key=True)
posted = sqlalchemy.Column(
sqlalchemy.DateTime(timezone=True),
nullable=False,
server_default=sqlalchemy.func.now()
)
content = sqlalchemy.Column(sqlalchemy.Text, nullable=False)
#m2o
user_id = sqlalchemy.Column(
sqlalchemy.Integer,
sqlalchemy.ForeignKey('users.user_id'),
nullable=False
)
user = sqlalchemy.orm.relationship(
'User',
uselist=False,
back_populates='comments',
lazy='joined'
)
post_id = sqlalchemy.Column(
sqlalchemy.Integer,
sqlalchemy.ForeignKey('posts.post_id'),
nullable=False
)
post = sqlalchemy.orm.relationship(
'Post',
uselist=False,
back_populates='comments',
lazy='joined'
)
def __repr__(self):
return f'Comment({self.comment_id!r}, {self.posted!r})'
def main():
engine = sqlalchemy.create_engine(
'postgresql+psycopg2:///stack',
echo=True,
server_side_cursors=True,
use_batch_mode=True
)
Base.metadata.create_all(engine)
Session = sqlalchemy.orm.sessionmaker(bind=engine)
session = Session()
session.commit()
try:
the_user = session.query(User).filter(User.username == 'example').one()
except sqlalchemy.orm.exc.NoResultFound:
the_user = User(
username='example',
email='example#example.com',
password=pbkdf2_sha256.hash('correct horse battery staple')
)
the_user.person = Person(first_name='Ex', middle_name='', last_name='Ample')
session.add(the_user)
print(the_user)
print(the_user.person)
if not the_user.posts:
the_user.posts.append(Post(title='First post', content='Lorem ipsum'))
session.commit()
print(the_user.posts[0])
if not the_user.posts[0].comments:
the_user.posts[0].comments.append(Comment(content='Me too', user=the_user))
session.commit()
print(the_user.posts[0].comments[0])
if __name__ == '__main__':
main()
Several comments:
I don't think it is easy to have foreign-keys both ways for a mandatory one-to-one relationship.
I made both User and Person use the same id numbers, as they are one-to-one.
I made the PostgreSQL now() as the default value for timestamps, instead of client-side utcnow.
I made the timestamps use "timestamp with timezone" type - the "timestamp" type (without timezone) is an abomination.
"user" is a bad name for a table, as this is also a keyword in PostgreSQL, so I changed it to "users". Other tables also changed to plural form for consistency.
A secure password storage is a must.
I used back_populates consistently, as it is more explicit and works better with static code analyzers than backref.