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How would you implement a type-validating descriptor that enforces a specific type constraint, reusable across multiple attributes and classes? How does Python's own implementation of instance methods use the descriptor protocol to achieve automatic 'self' binding? How do you implement a descriptor-based ORM-style field that lazily loads related data only when actually accessed? How would you write a descriptor supporting attribute DELETION via __delete__, and what real use case does that enable? How would you use a WeakKeyDictionary inside a descriptor to store per-instance data without relying on the instance's own __dict__ or requiring a dedicated __slots__ entry? How does @property's read-only behavior (no setter defined) actually raise an AttributeError, and how would you customize that error message?
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How do properties and descriptors interact with __slots__, and what special consideration is needed?

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Answer

A descriptor (including @property) works fine as a CLASS attribute alongside __slots__, since the descriptor ITSELF lives on the class, not the instance — but a custom descriptor's __get__/__set__ implementation CAN'T use a plain instance.__dict__ for storage (since __slots__ removes __dict__ entirely) and must instead store data in a DEDICATED slot or a WeakKeyDictionary keyed by instance.
class Point:
    __slots__ = ("_x",)  # explicit slot for internal storage
    @property
    def x(self):
        return self._x
    @x.setter
    def x(self, value):
        self._x = value  # stored in the '_x' slot, not a __dict__ (which doesn't exist)

p = Point()
p.x = 5
print(p.x)  # 5
Real-world example Combining @property-based validation with __slots__-based memory optimization for a class expected to have millions of instances.

Common follow-ups: How would a generic, reusable descriptor (not using @property) need to store per-instance data when the class uses __slots__?

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All 15 Descriptors & Properties questions