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24-class-metaprog/bulkfood/README.md

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+# Legacy Class Descriptor and Metaclass Examples
+
+Examples from _Fluent Python, First Edition_—Chapter 21, _Class Metaprogramming_,
+that are mentioned in _Fluent Python, Second Edition_—Chapter 25, _Class Metaprogramming_.
+
+These examples were developed with Python 3.4.
+They run correctly in Python 3.9, but now it is easier to fullfill the same requirements
+without resorting to class decorators or metaclasses.
+
+I have preserved them here as examples of class metaprogramming techniques
+that you may find in legacy code, and that can be refactored to simpler code
+using a base class with `__init_subclass__` and decorators implementing `__set_name__`.
+
+## Suggested Exercise
+
+If you'd like to practice the concepts presented in chapters 24 and 25 of
+_Fluent Python, Second Edition_,
+you may to refactor the most advanced example, `model_v8.py` with these changes:
+
+1. Simplify the `AutoStorage` descriptor by implementing `__set_name__`.
+This will allow you to simplify the `EntityMeta` metaclass as well.
+
+2. Rewrite the `Entity` class to use `__init_subclass__` instead of the `EntityMeta` metaclass—which you can then delete.
+
+Nothing should change in the `bulkfood_v8.py` code, and its doctests should still pass.
+
+To run the doctests while refactoring, it's often convenient to pass the `-f` option,
+to exit the test runner on the first failing test.
+
+```
+$ python3 -m doctest -f bulkfood_v8.py
+```
+
+Enjoy!