And I patiently continue this thread, hoping that people whose argument
would be along the lines of "I teach Python, and I don't want to teach
my students 2 ways of doing the same thing, and which way use when. Why,
if PEP634 offers just one way?"
They don't do the same thing, though. One does traditional duck typing (checking for the presence of a specified set of attributes on an object), while the other matches a sequence of attributes specified by the class.
PEP 634 just conflates the two tasks into a single call-like syntax that may or may not bare any resemblance to the type's constructor signature.
Cheers,
Nick.