[Python-ideas] Improving the expressivity of function annotations

[Masklinn]

On 2011-04-04, at 10:44 , Carl M. Johnson wrote:
> It wouldn't be that hard to make a class decorator that would work like:
> 
> @interface
> class Duck:
>    def quack(): pass
>    def walk(): pass
> 
> class Mallard:
>   def quack():
>       print("quack")
>   def walk():
>       print("waddle")
> 
> assert issubclass(Mallard, Duck) #Passes.
> 
> Where "interface" is a loose term like Go, and anything with the
> relevant methods counts as a subclass. It would probably make sense to
> add something like that to the abc module.

The "issue" is roughly the same as for abcs, in that you still have to give a name (and pre-define a type) for something which may not warrant it, and this naming may even serve to muddy the water some cases when used in type signatures (see Mapping abc example)

Otherwise, sure.