Is it normal not to understand every line of code in a Flask tutorial?

It’s fine to continue while you’re still filling in gaps, but don’t become comfortable with never understanding them. In particular, make an effort to learn unfamiliar Python syntax, standard-library features, and the Flask concepts that your application depends on. You don’t need to understand every implementation detail of every imported library, but you should understand the code you maintain, troubleshoot, or deploy.

A good way to learn is to get the tutorial working, then experiment with it. Change a value, remove a line, alter the output, or replace a function and observe what breaks. Follow up on the questions that come up. You’ll learn more by testing your assumptions than by trying to memorize every line before moving on.

That’s completely normal, especially the first time you work through an unfamiliar codebase. With experience, more patterns and syntax will become intuitive, but you’ll always encounter unfamiliar code in new projects. Keep notes about the parts you don’t understand and return to them when you have time.

Programming is built on layers of abstraction, so nobody understands every detail of everything their code relies on. Even experienced developers use documentation and tools to explain unfamiliar code. Tools such as language models can help explain a snippet, but check the explanation carefully and make sure you can describe what the code does before depending on it in a real project.

There’s a useful distinction between learning code and shipping code. While learning, it’s perfectly reasonable to write code you only partly understand and investigate it as you go. Before other people rely on the application, though, you should understand the important parts well enough to maintain, debug, and secure them. The goal isn’t instant total understanding; it’s steadily reducing the unknowns.