How can I study programming textbooks so the knowledge actually sticks?

Build small projects around what you are learning. If you're studying arrays or dictionaries, make a simple inventory; if you're learning functions, split the project into reusable pieces. Keep the projects small and experiment with edge cases. Programming knowledge becomes much easier to recall when you repeatedly pull it out to solve a real problem.

Rewrite important ideas in your own words as if you were explaining them to someone who knows nothing. For practical syntax, write code; for theory, make short summaries or diagrams. Reading out loud or explaining the concept to an imaginary person can also expose gaps in your understanding.

Use spaced repetition instead of trying to memorize an entire chapter in one sitting. Review the main ideas the next day, then again after a week and later in the month. You don't need to remember every line of a textbook—aim to understand the concepts and remember enough to know what to revisit when a project requires them.

The biggest thing is to apply every concept immediately. After reading about loops, arrays, or linked lists, close the book and write a small program from memory. Try adding, removing, sorting, or testing things yourself instead of only following the examples. Making mistakes and debugging them is what helps the ideas stick.

Don't skip the exercises, even when they seem repetitive. Read a section, look away from the book, and explain or recreate the idea without checking your notes. When you get stuck, look up only what you need, then try again. That struggle shows you exactly what you haven't learned yet.