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

[Steven D'Aprano]

On Fri, Aug 05, 2016 at 11:03:55PM +0200, Sven R. Kunze wrote:

> Will arbitrary expressions work or only type declarations?
> 
> a: <expression>

My understanding is that the Python interpreter will treat the part 
after the colon as a no-op. So long as it is syntactically valid, it 
will be ignored, and never evaluated at all.


# Okay
spam: fe + fi * fo - fum

# SyntaxError
spam: fe fi fo fum


But the type-checker (if any) should be expected to complain bitterly 
about anything it doesn't understand, and rightly so. I think that this 
form of variable annotation should be officially reserved for type 
hints, and only type hints.


-- 
Steve