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How Python’s Descriptor Protocol Implements Attribute Access
- The descriptor protocol is a fundamental mechanism in Python that governs how attribute access — retrieval, assignment, and deletion — is handled.
- It operates through a set of specially defined methods that are implemented in a class, enabling precise control over the behavior of attributes.
- These methods, __get__, __set__, and __delete__, are invoked automatically during attribute access operations when a descriptor object
- __get__ method when obj.attr is accessed. This overrides the default behavior of retrieving the value directly from the instance's __dict__.
- When an attribute is accessed, Python executes a series of well-defined steps to resolve the attribute's value.
- Descriptors are typically defined at the class level, meaning they exist as part of the class definition
- A descriptor is classified as a data descriptor if it defines the __set__ method or the __delete__ method
- data descriptors, by implementing __set__, control both retrieval and assignment of attributes, bypassing the instance’s __dict__.
- non-data descriptors, which lack __set__, allow instance attributes to take priority over the descriptor.
- This architecture underpins many core Python features, such as property objects and method binding, offering fine-grained control over how attributes behave.
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