👀 Views: 64 💬 Answers: 1 📅 Created: 2025-06-13

python-3.x flask sqlalchemy flask-sqlalchemy Python

I'm writing unit tests and Could someone explain I'm trying to debug Hey everyone, I'm running into an issue that's driving me crazy..... I'm working with an scenario where a nested transaction fails to commit properly when using Flask-SQLAlchemy in my Python 3.11 application. I have a structure where I attempt to create a new user and then log this action in a separate table within a single request. When I try to commit the changes, I receive the following behavior: ``` sqlalchemy.exc.InvalidRequestError: A transaction is already begun. ``` I've tried explicitly managing the session using `session.begin_nested()`, but the same behavior continues. Here's a simplified version of my code: ```python from flask import Flask, request from flask_sqlalchemy import SQLAlchemy app = Flask(__name__) app.config['SQLALCHEMY_DATABASE_URI'] = 'sqlite:///test.db' db = SQLAlchemy(app) class User(db.Model): id = db.Column(db.Integer, primary_key=True) name = db.Column(db.String(50)) class ActionLog(db.Model): id = db.Column(db.Integer, primary_key=True) action = db.Column(db.String(100)) @app.route('/create_user', methods=['POST']) def create_user(): data = request.json user = User(name=data['name']) with db.session.begin_nested(): # Trying to use nested transaction db.session.add(user) action_log = ActionLog(action=f'Created user {data['name']}') db.session.add(action_log) # Here I suspect the question may arise db.session.commit() # This commit fails return 'User created successfully', 201 if __name__ == '__main__': db.create_all() # Ensure tables are created app.run(debug=True) ``` I've verified that the database is accessible and that my models are correctly defined. I also checked for any existing transactions before this code runs. Why is the nested transaction causing issues, and how can I properly handle this situation? Any insights would be greatly appreciated! My development environment is Ubuntu. Any ideas what could be causing this? Thanks in advance! I'm working in a Ubuntu 22.04 environment.