On 2 September 2016 at 02:21, Steven D'Aprano <st...@pearwood.info> wrote:
> 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
None already has a meaning as an annotation - it's a shorthand for "type(None)".
While for variables and parameters, that's usually only seen in
combination with Union, and even though Union[T, None] has a preferred
spelling as Optional[T], there's also the "-> None" case to specify
that a function doesn't return a value. Having "-> None" mean "no
return value" and "NAME: None" mean "infer type from later assignment"
would be quite confusing.
However, a standalone Ellipsis doesn't currently have a meaning as a
type annotation (it's only meaningful when subscripting Tuple and
Callable), so a spelling like this might work:
NAME: ...
That spelling could then also be used in function definitions to say
"infer the return type from the return statements rather than assuming
Any":
def inferred_return_type(): -> ...
return some_other_function()
Cheers,
Nick.
--
Nick Coghlan | ncogh...@gmail.com | Brisbane, Australia
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