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Lesson 23 — Descriptors
Control attribute access
A descriptor is a class with get/set that manages another class's attribute. set runs on every assignment, so it can validate.
Why it matters: it is how ORMs and @property work under the hood.
Finish __set__: raise ValueError("must be >= 0") for negatives, otherwise store the value with setattr.
Run your code — when the output matches the task, you will see a green check. Then mark the lesson complete.
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