[Python] Flask SQLAlchemy MySQL Connection Issue – Connectivity & Connection String Issue

I'm developing a Flask application using Flask-SQLAlchemy and MySQL, but I'm facing issues with both database connectivity and correctly forming the connection string.

Setup Details:

• Backend: Flask
• ORM: SQLAlchemy
• Database: MySQL (local 9.2.0 and docker compose version 8)
• Driver: mysql+pymysql

Connection String I'm Using:

class Config:
SQLALCHEMY_DATABASE_URI = (
f"mysql+pymysql://{os.getenv('MYSQL_USER')}:{os.getenv('MYSQL_PASSWORD')}"
f"@{os.getenv('MYSQL_HOST')}:{os.getenv('MYSQL_PORT')}/{os.getenv('MYSQL_DB')}"
)
SQLALCHEMY_TRACK_MODIFICATIONS = False
SECRET_KEY = os.getenv("SECRET_KEY")


Error Message:

• I get one of the following errors when running my Flask app while running API locally:

Traceback (most recent call last): File "/Users/aravindkoniki/Documents/Workspace/Git Respositories/github/CloudScaler/api/auth_service/wsgi.py", line 4, in app = create_app() File "/Users/aravindkoniki/Documents/Workspace/Git Respositories/github/CloudScaler/api/auth_service/app/init.py", line 12, in create_app db.init_app(app) File "/Users/aravindkoniki/Documents/Workspace/Git Respositories/github/CloudScaler/api/auth_service/venv/lib/python3.9/site-packages/flask_sqlalchemy/extension.py", line 373, in init_app self._apply_driver_defaults(options, app) File "/Users/aravindkoniki/Documents/Workspace/Git Respositories/github/CloudScaler/api/auth_service/venv/lib/python3.9/site-packages/flask_sqlalchemy/extension.py", line 607, in _apply_driver_defaults url = sa.engine.make_url(options["url"]) File "/Users/aravindkoniki/Documents/Workspace/Git Respositories/github/CloudScaler/api/auth_service/venv/lib/python3.9/site-packages/sqlalchemy/engine/url.py", line 856, in make_url return _parse_url(name_or_url) File "/Users/aravindkoniki/Documents/Workspace/Git Respositories/github/CloudScaler/api/auth_service/venv/lib/python3.9/site-packages/sqlalchemy/engine/url.py", line 917, in _parse_url components["port"] = int(components["port"]) ValueError: invalid literal for int() with base 10: 'None'
​

• Connection refused while running from docker compose file

Troubleshooting Done So Far:

• 
  Verified MySQL is running and accessible from the machine.
  
  
• 
  Confirmed credentials and database exist.
  
  
• 
  Tested direct connection via MySQL CLI:
  
  mysql -u user -p -h host -P 3306 -D db_name
  

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