class LogMixin: def process(self): print("Logging start") super().process() print("Logging end")
: Intercept assignment and deletion to enforce validation or trigger side effects. The Descriptor Protocol
Python does not have true private attributes. Instead:
class Point: __slots__ = ('x', 'y') def __init__(self, x, y): self.x = x self.y = y python 3 deep dive part 4 oop high quality
You can view the MRO of any class by accessing its __mro__ attribute or calling the .mro() method.
This approach—sometimes called "duck typing" combined with protocol implementation—is a defining characteristic of idiomatic Python OOP. Instead of inheriting from abstract base classes (though those exist too), you simply implement the required methods, and Python's dynamic dispatch handles the rest.
For intermediate Python developers, there comes a point where basic syntax and beginner-level object-oriented concepts no longer suffice. You understand classes, instances, and inheritance—but you want more. You want to write production-ready code that is elegant, efficient, and maintainable. This is where a true deep dive becomes essential, and Fred Baptiste's Python 3: Deep Dive (Part 4 - OOP) course has become the definitive resource for developers seeking to elevate their Python OOP expertise. and ORM field definitions.
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Descriptors are the secret behind methods, static methods, class methods, and properties. A descriptor is a class that defines __get__ , __set__ , or __delete__ .
For those building frameworks or libraries, metaprogramming allows you to control how classes themselves are constructed. the appropriate descriptor method is called
def __set__(self, obj, value): self.validate(value) obj.__dict__[self.name] = value
abc module provides infrastructure for defining . An ABC cannot be instantiated and is meant to be subclassed. It can enforce that concrete subclasses implement certain methods by marking them with @abstractmethod . This is ideal for defining clear interfaces and contracts within your codebase.
When you access an attribute, Python's lookup chain checks whether the attribute is a descriptor. If it is, the appropriate descriptor method is called, giving the descriptor complete control over attribute access. This protocol enables elegant solutions for data validation, lazy evaluation, type checking, and ORM field definitions.