Class properties in Python 3.11+

In Python 3.9, we gained the ability to chain @classmethod and @property to sensibly create class properties.

class Foo:
  @property
  def instance_property(self):
    return "A regular property"

  @classmethod
  @property
  def class_property(cls):
    return "A class property"

This was enabled by giving @classmethod proper interaction with the descriptor protocol, meaning one's prospects were not limited to @property but any descriptor under the sun. Everything was fine and dandy until it was discovered that the implementation led to "a number of downstream problems", with deprecation coming in Python 3.11.

I've read over the GitHub discussions concerning the deprecation a bit and will not gripe here about what I would call a hasty retraction to a hasty design. The fact of the matter is that class properties are a reasonable thing that people want and could use in Python 3.9/3.10, but now can't. The release notes suggest the following:

To “pass-through” a classmethod, consider using the __wrapped__ attribute that was added in Python 3.10.

It would not be controversial to call such a sentence extremely unhelpful on its own. The descriptor protocol is not something your average user will ever need to or want to encounter, and thus chaining @classmethod with them via a custom implementation is surely something that those in the know could and would spend time figuring out how to properly do in 3.11+.

But for those who have no idea what @property is besides that thing that lets them drop parentheses, how do you define class properties in Python 3.11+, and, in particular, how do you do it well?

source https://stackoverflow.com/questions/76249636/class-properties-in-python-3-11