[Python-Dev] Please reject or postpone PEP 526

[Steven D'Aprano]

On Mon, Sep 05, 2016 at 04:40:08PM +0300, Koos Zevenhoven wrote:

> On Mon, Sep 5, 2016 at 3:10 PM, Steven D'Aprano <steve at pearwood.info> wrote:
> >
> > [Koos Zevenhoven]
> >> >> How is it going to help that these are equivalent within one checker,
> >> >> if the meaning may differ across checkers?
> >
> > Before I can give an answer to your [Koos'] question, I have to
> > understand what you see as the problem here.
> 
> The problem was that suggested restrictive addition into PEP 526 with
> no proper justification, especially since the PEP was not supposed to
> restrict the semantics of type checking. 

What "suggested restrictive addition into PEP 526" are you referring to?

Please be specific.


> I was asking how it would
> help to add that restriction. Very simple. Maybe some people got
> confused because I did want to *discuss* best practices for type
> checking elsewhere.

I still can't answer your question, because I don't understand what 
restriction you are talking about. Unless you mean the restriction that 
variable annotations are to mean the same thing whether they are written 
as `x:T = v` or `x = v #type: T`. I don't see this as a restriction.



> > The type comment systax is required for Python 2 and backwards-
> > compatibility. That's a given.
> 
> Sure, but all type checkers will not have to care about Python 2.

They will have to care about type comments until such time as they are 
ready to abandon all versions of Python older than 3.6.

And even then, there will probably be code still written with type 
comments until Python 4000.


-- 
Steve