[Python-Dev] Is static typing still optional?

[Eric V. Smith]

On 12/10/2017 5:00 PM, Raymond Hettinger wrote:
> 
> 
>> On Dec 10, 2017, at 1:37 PM, Eric V. Smith <eric at trueblade.com> wrote:
>>
>> On 12/10/2017 4:29 PM, Ivan Levkivskyi wrote:
>>> On 10 December 2017 at 22:24, Raymond Hettinger <raymond.hettinger at gmail.com<mailto:raymond.hettinger at gmail.com>> wrote:
>>>     Without typing (only the first currently works):
>>>          Point = namedtuple('Point', ['x', 'y', 'z'])          #
>>>     underlying store is a tuple
>>>          Point = make_dataclass('Point', ['x', 'y', 'z'])      #
>>>     underlying store is an instance dict
>>> Hm, I think this is a bug in implementation. The second form should also work.
>>
>> Agreed.
>>
>> I have a bunch of pending changes for dataclasses. I'll add this.
>>
>> Eric.
> 
> Thanks Eric and Ivan.  You're both very responsive.  I appreciate the enormous efforts you're putting in to getting this right.

Thank you for your feedback. It's very helpful.

I see a couple of options:
1a: Use a default type annotation, if one is not is supplied. typing.Any 
would presumably make the most sense.
1b: Use None if not type is supplied.
2: Rework the code to not require annotations at all.

I think I'd prefer 1a, since it's easy. However, typing is not currently 
imported by dataclasses.py. There's an argument that it really needs to 
be, and I should just bite the bullet and live with it. Possibly with 
Ivan's PEP 560 work my concern on importing typing goes away.

1b would be easy, but I don't like using non-types for annotations. 2 
would be okay, but then that would be the only time __annotations__ 
wouldn't be set on a dataclass.

> I suggest two other fix-ups:
> 
> 1) Let make_dataclass() pass through keyword arguments to _process_class(), so that this will work:
> 
>      Point = make_dataclass('Point', ['x', 'y', 'z'], order=True)

Agreed.

> 2) Change the default value for "hash" from "None" to "False".  This might take a little effort because there is currently an oddity where setting hash=False causes it to be hashable.  I'm pretty sure this wasn't intended ;-)

It's sufficiently confusing that I need to sit down when I have some 
free time and noodle this through. But it's still on my radar.

Eric.