Fix “invalid literal for int() with base 10: 'None'” in FastAPI (Asyncpg + Docker)

You're using Docker to deploy your FastAPI application with Aiven PostgreSQL, when all of a sudden you notice this traceback: ValueError: invalid literal for int() with base 10: 'None' It refers to SQLAlchemy's URL parser and complains that the string "-None" is the port portion of your database URL. Your URL appears as postgresql+asyncpg://user:pass@host:None/dbname . What caused that to occur? And above all, how do you fix it? In this tutorial, I'll walk you through the cause of this error and provide a clean solution. We'll also discuss best practices for managing environment variables in containerized FastAPI applications. Understanding the Error The error occurs when SQLAlchemy's make_url() function tries to parse the database URL and convert the port component to an integer, but receives the literal string "None" . This happens because somewhere in your code, you're building the URL with a variable that evaluates to None , and when interpolated into an f-string, None becomes the