[Python-ideas] Trial balloon: adding variable type declarations in support of PEP 484

[Ethan Furman]

On 08/04/2016 12:11 PM, Daniel Moisset wrote:

> I follow the example perfectly. Now suppose a reader finds the following
> piece of code:
>
> class Starship:
>      stats: class Dict[str, int] = {}  # Pure class variable
>      damage: class int = 0  # Hybrid class/instance variable
>      captain: str  # Pure instance variable
>      speed: float = 0
>
> I added a new attribute (similar to b in your original example). Given
> that the type declaration doesn't say "class",the reader might be
> inclined to think it's an instance variable. But in runtime (if I got
> you right), that variable will be stored in "Starship.__dict__" and
> writing "Starship.speed = 3" will change the speed of those starship
> instances that still haven't set the attribute.

The type checker should flag that as a bug, since Starship.speed is 
supposed to be an instance variable.

--
~Ethan~