Python is a high-level, object-oriented, interactive, interpreted, multipurpose, and versatile scripting programming language. Programmers and developers are using Python for creating big data applications, mobile applications, desktop software, data science, automation, and even web pages. Programmers are creating a number of projects to make impactful applications. It is a widely used language that has an easy syntax. It is also used for the relational database using SQL. SQLAlchemy is known as a library to communicate between Python and databases. It is basically the Python SQL toolkit that offers SQL flexibility to programmers and developers.
SQLAlchemy is also used as an ORM tool (Object Relational Mapper) used to translate classes of Python to tables on databases. When you are working with SQLAlchemy, you may experience the error “AttributeError: can’t set attribute when connecting to sqlite database with flask-sqlalchemy”. Check out how the error occurs
How do you get the error?
When you are working on a flask project, you get the error warning. Check out the code that results in the error
config.py file
import os
# load the environment variables from the .env file
from dotenv import load_dotenv
load_dotenv()
# Determine the folder of the top-level directory of this project
BASEDIR = os.path.abspath(os.path.dirname(__file__))
class Config:
FLASK_ENV = 'development'
TESTING = False
DEBUG = False
SECRET_KEY = os.getenv('SECRET_KEY', default='A very terrible secret key.')
SQLALCHEMY_DATABASE_URI = os.getenv('DATABASE_URL',
default=f"sqlite:///{os.path.join(BASEDIR, 'instance', 'app.db')}")
SQLALCHEMY_TRACK_MODIFICATIONS = False
class DevelopmentConfig(Config):
DEBUG = True
class TestingConfig(Config):
TESTING = True
SQLALCHEMY_DATABASE_URI = os.getenv('DATABASE_URL',
default=f"sqlite:///{os.path.join(BASEDIR, 'instance', 'test.db')}")
class ProductionConfig(Config):
FLASK_ENV = 'production'User model
from project import db, login_manager
from flask_login import UserMixin
from werkzeug.security import generate_password_hash, check_password_hash
class User(db.Model, UserMixin):
__tablename__ = 'users'
id = db.Column(db.Integer, primary_key=True)
username = db.Column(db.String, unique=True)
hashed_password = db.Column(db.String)
def __init__(self, username, password):
self.username = username
self.hashed_password = generate_password_hash(password)
def is_password_valid(self, password):
return check_password_hash(self.hashed_password, password)
def __repr__(self):
return '<User {}>'.format(self.id)
@login_manager.user_loader
def load_user(user_id):
return User.query.get(int(user_id))This program shows the error warning. Have a look at it
(env) PS C:\coding-projects\task-master-tdd> flask shell
Python 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:43:08) [MSC v.1926 32 bit (Intel)] on win32
App: project [development]
Instance: C:\coding-projects\task-master-tdd\instance
>>> from project import db
>>> db
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "c:\coding-projects\task-master-tdd\env\lib\site-packages\flask_sqlalchemy\__init__.py", line 1060, in __repr__
self.engine.url if self.app or current_app else None
File "c:\coding-projects\task-master-tdd\env\lib\site-packages\flask_sqlalchemy\__init__.py", line 943, in engine
return self.get_engine()
File "c:\coding-projects\task-master-tdd\env\lib\site-packages\flask_sqlalchemy\__init__.py", line 962, in get_engine
return connector.get_engine()
File "c:\coding-projects\task-master-tdd\env\lib\site-packages\flask_sqlalchemy\__init__.py", line 555, in get_engine
options = self.get_options(sa_url, echo)
File "c:\coding-projects\task-master-tdd\env\lib\site-packages\flask_sqlalchemy\__init__.py", line 570, in get_options
self._sa.apply_driver_hacks(self._app, sa_url, options)
File "c:\coding-projects\task-master-tdd\env\lib\site-packages\flask_sqlalchemy\__init__.py", line 914, in apply_driver_hacks
sa_url.database = os.path.join(app.root_path, sa_url.database)
AttributeError: can't set attribute
>>>How To Solve the Error “AttributeError: can’t set attribute when connecting to sqlite database with flask-sqlalchemy”
We have a few solutions that can help you resolve the error efficiently
Solution 1 – Downgrade the version of SQLAlchemy
The simplest solution to sort out the error is to downgrade the SQLAlchemy version. You need to follow the below steps to successfully downgrade the version
- Use the pip freeze command to be double sure that the issue is affecting or not
- You get to know that the SQLAlchemy current version is 1.4.0.
- The best way is to manually downgrade the version using the below command
pip install SQLAlchemy==1.3.23This is how you can simply resolve the error.
Solution 2 – Pinning SQLAlchemy
Another way to fix the error is to pin the SQLAlchemy lower version than 1.4.0. To do that, follow the below steps
To freeze the package
pip freeze > requirements.txtIn the requirements.txt, upgrade SQLAlchemy
SQLAlchemy<1.4.0In order to reinstall packages, use the below command
pip install -r requirements.txtSolution 3 – Check if the version is updated automatically
Sometimes the auto updates cause the error. SQLALchemy works as a dependency by auto-installing for Flask-SQLAlchemy. The latest version (1.4.0) brought the below change
The URL object is now an immutable named tuple. To modify a URL object, use the URL.set() method to produce a new URL object.To fix the error, you just need to install the version you previously had.
Conclusion
We shed light on the solutions to help you fix the error “AttributeError: can’t set attribute when connecting to sqlite database with flask-sqlalchemy”. I hope you find it helpful!
