[Python-ideas] A proper way to bring real interfaces to Python

[Ryan Gonzalez]

Worth maybe noting that this could play interestingly with PEP 484?

--
Ryan (ライアン)
Yoko Shimomura, ryo (supercell/EGOIST), Hiroyuki Sawano >> everyone else
https://refi64.com/
On May 4, 2019, 8:24 PM -0500, Serge Matveenko <s at matveenko.ru>, wrote:
> Hi, all!
>
> I believe, almost everybody is familiar with the `abc` package.
>
> The problem is that the ABC class is not a separate thing from
> `object`. So, using ABCs often results in complicated inheritance
> designs and even in the infamous metaclass conflict.
>
> Another problem is that ABC performs checks at the moment an object is
> being instantiated which isn't exactly the way one expects an
> interface to work. The obvious way would be to enforce the
> implementation at the moment `type` for that class is created, i.e. on
> module execution time.
>
> I'm aware there was `PEP 245 -- Python Interface Syntax` which was
> rejected. However, I agree with the idea that the syntax proposed in
> this PEP wasn't particularly "pythonish".
>
> So, I would like to propose adding a third main object called
> `interface` in addition to `object` and `type` and to use it to define
> interface objects. Such interfaces could then be used in the class
> definition in the following way.
>
> ```
> class MyInterfaceA(interface):
> def foo():
> pass
>
> class MyInterfaceB(interface):
> def bar():
> pass
>
> class Implementation(implements=[MyInterfaceA, MyInterfaceB]):
> def foo():
> pass
> def bar():
> pass
> ```
>
> As a proof of concept, I've implemented a library which implements the
> idea and allows to use this approach right out of the box —
> https://pypi.org/project/strict-interfaces/.
>
> I would like to get any feedback for the idea and the library.
>
> Thanks to all!
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