[Python-Dev] Is static typing still optional?

[Stephan Hoyer]

On Thu, Dec 21, 2017 at 6:39 AM Ivan Levkivskyi <levkivskyi at gmail.com>
wrote:

> For me, the three options for "don't care" have a bit different meaning:
>
> * typing.Any: this class is supposed to be used with static type checkers,
> but this field is too dynamic
> * ... (ellipsis): this class may or may not be used with static type
> checkers, use the inferred type in the latter case
> * "field docstring": this class should not be used with static type
> checkers
>
> Assuming this, the second option would be the "real" "don't care". If this
> makes sense,
> then we can go the way proposed in
> https://github.com/python/typing/issues/276 and make ellipsis semantics
> "official" in PEP 484.
> (pending Guido's approval)
>

I am a little nervous about using "..." for inferred types, because it
could potentially cause confusion with other uses of ellipsis in typing.

Ellipsis already has a special meaning for Tuple, so an annotation like
MyClass[int, ...] could mean either a tuple subclass with integer elements
or a two argument generic type where the second type is inferred. Actually,
it's ambiguous even for Tuple.

Ellipsis could also make a lot of sense for typing multi-dimensional arrays
similar to how it's used in indexing to denote "any number of dimensions."
Again, the semantics for "..." might defer from "an inferred size."

>
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