[Python-Dev] PEP 526 ready for review: Syntax for Variable and Attribute Annotations

[Ivan Levkivskyi]

On 1 September 2016 at 18:21, Steven D'Aprano <steve at pearwood.info> wrote:

> The simplest way would be to say "go on, one type hint won't hurt,
> there's no meaningful runtime cost, just do it".
>
> from typing import Any
>
> class X:
>     NAME: Any
>
> Since I'm not running a type checker, it doesn't matter what hint I use,
> but Any is probably the least inaccurate.
>
> But I think there's a better way.
>
> Unless I've missed something, there's no way to pre-declare an instance
> attribute without specifying a type. (Even if that type is Any.) So how
> about we allow None as a type-hint on its own:
>
>     NAME: None
>
> as equivalent to a declaration *without* a hint. The reader, and the
> type-checker, can see that there's an instance attribute called NAME,
> but in the absense of an actual hint, the type will have to be inferred,
> just as if it wasn't declared at all.
>

There is a convention for function annotations in PEP 484 that a missing
annotation
is equivalent to Any, so that I like your first option more.

--
Ivan
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