I open my terminal to construct my data base with SQLAlchemy , in python
The error is in the following code:
from flask import Flask, render_template
#import SQLALchemy
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
#set the SQLALCHEMY_DATABASE_URI key
app.config['SQLALCHEMY_DATABASE_URI']= 'sqlite:///song_library.db'
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
app.config['SECRET_KEY'] = 'you-will-never-guess'
#create an SQLAlchemy object named `db` and bind it to your app
db = SQLAlchemy(app)
class Item(db.Model):
id = db.Column(db.Integer, primary_key=True)
playlist_id = db.Column(db.Integer, db.ForeignKey('Playlist.id'))
song_id = db.Column(db.Integer, db.ForeignKey('Song.id'))
#create the Playlist model here + add a nice representation method
class Playlist(db.Model):
id = db.Column(db.Integer, primary_key=True)
items = db.relationship('Item', backref='playlist', lazy='dynamic')
so after :
> python3
> from app import db
> from models import *
> db.create_all()
the following error raise:
sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'user.playlist_id' could not find table 'Playlist' with which to generate a foreign key to target column 'id'
what should I do to solve it?
Related
from wsgiref.util import request_uri
from flask import Flask, render_template, request, redirect
from flask_sqlalchemy import SQLAlchemy
from datetime import datetime
from sqlalchemy.orm import declarative_base, relationship
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = "sqlite:///todo.db"
app.config['SQLALCHEMY_TRACK_MODIFICATIONS'] = False
db = SQLAlchemy(app)
class List(db.Model):
listid=db.Column(db.Integer,primary_key=True)
namelist= db.Column(db.String(200), primary_key=True,nullable=False)
class Card(db.Model):
listid=db.Column(db.Integer,db.ForeignKey("list.listid"),nullable=False)
namelist=db.Column(db.Integer,db.ForeignKey("list.namelist"),nullable=False)
Title = db.Column(db.String(200), primary_key=True,nullable=False)
Content = db.Column(db.String(500), nullable=False)
Deadline = db.Column(db.Date)
if __name__ == "__main__":
app.run(debug=True)
When I am creating the database using one foreign key from the List table my code is working fine but whenever I am recreating my database and using two foreign keys in my Card table, I am unable to populate my database.
Mistake is "namelist" is Integer type, but reference column list.namelist is String(200)
class Card(db.Model):
...
namelist = db.Column(db.String(200), db.ForeignKey("list.namelist"), nullable=False)
...
I have created a models.py file describing my schema. I am using the code below to create the DB and initialize it with the model.py schema. When I call the create_app function a new sqlite file gets create but it is empty. It is not picking up the schema from my models.py file.
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from sqlalchemy_utils.functions import database_exists
db = SQLAlchemy()
DB_NAME = "database.db"
def create_app():
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = f'sqlite:///{DB_NAME}'
if not database_exists(app.config['SQLALCHEMY_DATABASE_URI']):
db.init_app(app)
db.create_all(app=app)
print(f'Created Database Successfully!!')
return app
models.py
from .main import db
from flask_login import UserMixin
from sqlalchemy.sql import func
class User(db.Model, UserMixin):
id = db.Column(db.Integer, primary_key=True)
email = db.Column(db.String(150), unique=True)
password = db.Column(db.String(150))
first_name = db.Column(db.String(150))
happened to me with missing init.py file in the package, maybe thats the case
After I imported the models file first, the DB was created sucessfully.
I'm working with flask and trying to learn sqlalchemy, I have a database where I added a third table to make a new feature, but the entire project stopped working, it says:
sqlalchemy.exc.NoReferencedTableError: Foreign key associated with column 'url_reference.folder_rel' could not find table 'reffolders' with which to generate a foreign key to target column 'id'
this is the dbs.py
from . import db
from flask_login import UserMixin
from sqlalchemy.sql import func
class User(db.Model, UserMixin):
id = db.Column(db.Integer, primary_key=True)
email = db.Column(db.String(200), unique=True)
user_password = db.Column(db.String(150))
user_name = db.Column(db.String(400))
user_refs = db.relationship("RefFolders")
class RefFolders(db.Model):
id = db.Column(db.Integer, primary_key=True)
folder_title = db.Column(db.String(1000))
date_added = db.Column(db.DateTime(timezone=True), default=func.now())
user_rel = db.Column(db.Integer, db.ForeignKey("user.id"))
url_rel = db.relationship("UrlReference")
class UrlReference(db.Model):
id = db.Column(db.Integer, primary_key=True)
ref_title = db.Column(db.String(1000))
ref_url = db.Column(db.String(30000))
date_added = db.Column(db.DateTime(timezone=True), default=func.now())
folder_rel = db.Column(db.Integer, db.ForeignKey("reffolders.id"))
this is where I make the database in the __init__.py:
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from os import path
from flask_login import LoginManager
db = SQLAlchemy()
DB_NAME = "database.db"
def app():
app = Flask(__name__)
app.config['SECRET_KEY'] = '<here is the key in my code>'
app.config['SQLALCHEMY_DATABASE_URI'] = f"sqlite:///{DB_NAME}"
db.init_app(app)
# making the blueprints usable
from .views import views
from .auth import auth
app.register_blueprint(views, url_prefix="/")
app.register_blueprint(auth, url_prefix="/")
from .dbs import User
from .dbs import UrlReference
from .dbs import RefFolders
db_create(app)
# Login manager
login_manager= LoginManager()
login_manager.login_view = 'views.home'
login_manager.init_app(app)
# Searching and loading user
#login_manager.user_loader
def load_user(id):
return User.query.get(int(id))
return app
def db_create(app):
if not path.exists("project/" + DB_NAME):
db.create_all(app=app)
I don't know what happened, maybe a problem with having a double foreign key?
I think flask or its extension guesses the table name you want, like CamelCase --> camel_case.
So in this case the tablename is probably ref_folders. You might want to just use tablename to set the table name yourself although I think their default is a good convention.
As a side note I would recommend using _id for your ids otherwise things might get pretty confusing between object relations and actual ids, ie. use user_id instead of user_rel in RefFolders.
SEE:
https://flask-sqlalchemy.palletsprojects.com/en/2.x/models/#declaring-models
Some parts that are required in SQLAlchemy are optional in
Flask-SQLAlchemy. For instance the table name is automatically set for
you unless overridden. It’s derived from the class name converted to
lowercase and with “CamelCase” converted to “camel_case”. To override
the table name, set the __tablename__ class attribute.
i have a project where i create four tables (users,products, agents, customer) when i do migration with:
flask db init,
flask db migrate,
flask db upgrade,
only users and products get migrated
here it is the structure of my project:
my code for user model is:
from main.extensions import db
from main.shared.base_model import BaseModel, HasCreatedAt,
HasUpdatedAt
class User(BaseModel, HasCreatedAt, HasUpdatedAt):
tablename = 'users'
id = db.Column(db.Integer, primary_key=True)
email = db.Column(db.String, unique=True, nullable=False)
password = db.Column(db.String, nullable=False)
phone = db.Column(db.Integer)
my code for every module starting by agent model:
from main.extensions import db
class Agent(db.Model):
__tablename__ = 'agents'
id = db.Column(db.Integer, primary_key=True)
picture = db.Column(db.String)
def __init__(self,email, password, phone, picture):
self.email = email
self.password=password
self.phone=phone
self.picture=picture
and for the model in customer is:
from main.modules.user.models import User
from main.extensions import db
class Customer(User):
__tablename__ = 'customers'
approved = db.Column(db.Boolean)
picture = db.Column(db.String)
def __init__(self, email, password, phone, picture, approved):
self.approved = approved
self.picture = picture
User.__init__(self,email,password,phone)
and finnaly the products model has:
from main.extensions import db
from main.shared.base_model import BaseModel, HasCreatedAt, HasUpdatedAt
class Product(BaseModel, HasCreatedAt, HasUpdatedAt):
__tablename__ = 'products'
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String, nullable=False)
the settings.py contains the following code:
and this init files for every model contains this code:
for the user __init.py:
from main.modules.users.api import blueprint as api
for the customer __init.py:
from main.modules.customer.api import blueprint as api
for the agent__init.py:
from main.modules.agent.api import blueprint as api
for the prodcut__init.py:
from main.modules.product.api import blueprint as api
import os
class DevSettings(Settings):
DEBUG = True
basedir = os.path.abspath(os.path.dirname(__file__))
SQLALCHEMY_DATABASE_URI="sqlite:///" + os.path.join(basedir, "data.sqlite")
SQLALCHEMY_TRACK_MODIFICATIONS=False
and the extension.py contains:
from flask_migrate import Migrate
from flask_sqlalchemy import SQLAlchemy
db = SQLAlchemy()
migrate = Migrate()
and the app.py contains this:
from flask import Flask, Blueprint
from main.extensions import db, migrate
from main.modules import product, agent, customer, user
from main.settings import DevSettings
MODULES = [ agent, customer,product, user]
main = Blueprint('main', __name__)
def create_app(settings=DevSettings):
app = Flask(__name__)
# Utiliser la configuration (settings).
app.config.from_object(settings)
app.config['SECRET_KEY'] = 'mysecretkey'
# On initialise les libraries Python.
# Init SQLAlchemy.
db.init_app(app)
# Init Migrate.
migrate.init_app(app, db)
app.register_blueprint(main)
register_modules(app)
return app
def register_modules(app):
for m in MODULES:
if hasattr(m, 'api'):
app.register_blueprint(m.api)
I am trying to use this code to add a table to a database in a Flask app on localhost - but it does not work. What should I do?
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI']='postgresql://postgres:123#localhost:5432/postgres'
db = SQLAlchemy(app)
class Person(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(), nullable=False)
db.create_all()
I changed my app name from "flask-hello-app" to "app"
and typed these 3 commands in terminal:
python
from app import db
db.create_all()
and it worked for me.
db.session.commit()
Good luck.
I just try your code using both Postgres and MySQL
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://root:55665566#localhost:5432/test'
db = SQLAlchemy(app)
class User(db.Model):
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String(80), unique=True, nullable=False)
email = db.Column(db.String(120), unique=True, nullable=False)
# from yourapplication import db
db.create_all()
Since I have created the table successfully,
I suggest you check some details below
Check the role attribute for the account.
Check the connection to the database, using command \du to confirm your accounts info, suppose you need to create a user 'postgres' which should show up in the table above.