This should be worked into a PEP, instead of living on as a bunch of python-ideas posts and blogs.
I find the attrs documentation (and Glyph's blog post about it) almost unreadable because of the exalted language -- half the doc seems to be *selling* the library more than *explaining* it. If this style were to become common I would find it a disturbing trend.
But having something alongside NamedTuple that helps you declare classes with mutable attributes using the new PEP 526 syntax (and maybe a few variants) would definitely be useful. Will someone please write a PEP? Very few of the specifics of attrs need be retained (its punny naming choices are too much for the stdlib).
Based on my thinking on the topic while writing my blog post, the tricky bit is going to be deciding how to handle default values (i.e. if you set a default value like `attr: int = 42` on the class definition then you have `cls.attr` exist which might not be what you want if you would rather have the default value explicitly set on every instance but not fall through to the class (e.g. `del ins.attr; ins.attr` raises an AttributeError instead of falling through to `cls.attr`). You could remove the default from the class in your __init_subclass__(), but then you have to decide if that's too unexpected/magical for someone looking at the code.
And I too would be interested in seeing something like this, if for any other reason than to help people not to misuse NamedTuple for quick-and-dirty data objects in new APIs (NamedTuple is meant to help move old-style tuple-based APIs to a class-based one).
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