typing.Final actually means something like "cannot be reassigned", whereas constant variable means "cannot change". Consider e.g.
class Spam: def __init__(self): self.eggs = 0
@final # method cannot be overridden (which is more related to "reassignment" than to "change") def more(self): self.eggs += 1
spam: Final[Spam] = Spam() spam.more() # This is allowed, but spam changed del spam # Allowed as well
Moreover, `Final` is part of typing, which is strange because it indicates a property of the variable name itself, not of its type. Perhaps the constant keyword can become a replacement for the confusing `typing.Final`.
So "constant" is semantically different than `typing.Final` (and `typing.final`), and it makes more sense to have it be a keyword (e.g. `constant spam`), instead of it being an annotation; it only should be used when declaring variables and attributes (e.g. `def f(a: Final)` is not allowed).