Just a friendly reminder that the window to get this in to 3.8 is closing.
The implementation in typing_extensions is pretty simple; upstreaming it will be easy. Also on a personal level: I'm in between big projects at work, now is a good time for me to work on it.

The backport (to python versions prior to pep_560) is proving a bit more challenging and I doubt we'll be able to get all the functionalities. I'm still trying to figure out the best way to proceed.

Best,
Till

On Tue, May 28, 2019 at 12:24 PM Jakub Stasiak <jakub@stasiak.at> wrote:

> On 28 May 2019, at 17:58, Till <till.varoquaux@gmail.com> wrote:
>
> Thanks Jakub,
> You're right __origin__ should point to `Annotated`. I created a pull
> request (https://github.com/python/typing/pull/635) that should
> address that. Also:
>
> def fun(x: List[Annotated[int, ‘some marker’]])
>
> is definitely valid.
>
> On Tue, May 28, 2019 at 9:01 AM Jakub Stasiak <jakub@stasiak.at> wrote:
>>
>>
>>
>>> On 28 May 2019, at 14:53, Jakub Stasiak <jakub@stasiak.at> wrote:
>>>
>>>
>>>
>>>> On 28 May 2019, at 11:52, Ivan Levkivskyi <levkivskyi@gmail.com> wrote:
>>>>
>>>> On Tue, 28 May 2019 at 04:37, Till <till.varoquaux@gmail.com> wrote:
>>>> I didn't implement any good helper function because I couldn't figure
>>>> out the idiomatic way to traverse type hints at runtime. It would be
>>>> very easy to add a "get_extras(t: typing.<Type>) -> Tuple[Any, ...]"
>>>> function. Would that work?
>>>>
>>>> This reminds me about something I wanted to do for Python 3.8: there is an idea to add couple public helpers for introspection of typing objects.
>>>> For example `get_origin()` and `get_args()`. That would essentially just thin public wrappers around private `__origin__`/`__args__` API.
>>>>
>>>> With such API one will be able to just write `if get_origin(typ) is Annotated: ...`
>>>>
>>>> --
>>>> Ivan
>>>>
>>>>
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>>>
>>> This actually gave me the idea to test
>>>
>>> x.__origin__ is Annotated
>>>
>>> instead of
>>>
>>> isinstance(x, _Annotated)
>>>
>>> but with the current implementation _Annotated.__origin__ points to the type being annotated, not the Annotated class. I made a dirty typing_extensions pull request[1] that attempts to rectify this but I’m not sure i’ll be able to finish it myself right now.
>>>
>>> On an unrelated note, something I’ve been wondering about since yesterday – is Annotated supposed to be, in principle, allowed to be used like this?
>>>
>>> def fun(x: List[Annotated[int, ‘some marker’]])
>>>
>>> Best,
>>> Jakub
>>>
>>> [1] https://github.com/python/typing/pull/634
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>>
>> PS. Apologies for ignoring your question regarding hypothetical get_extras function Till – I don’t have an opinion on it at the moment, doing things “manually” is fine for my purposes.
>>
>> Jakub


Cool, the code from your pull request works for me. I don’t think I have any other concernes or questions.

Jakub