How to correctly implement type `AList` for custom class `alist`, similiar to `List` and `list`

Question

How can I achieve the same with custom class alist and its type alias AList as how builtin list and List from typing work?

I can see that type List is defined following way in typing: List = _alias(list, 1, inst=False, name='List')

_alias is alias for internal class _SpecialGenericAlias and AFAIK those should not be used externally.

I have now following code:

import asyncio
from typing import Generic, TypeVar

T = TypeVar("T")


class alist(list, Generic[T]):  # pylint: disable=invalid-name
    async def __aiter__(self):
        for _ in self:
            yield _


AList = alist[T]


async def func(integers: AList[int]):
    async for integer in integers:
        print(integer)


asyncio.run(func(alist([1, 2, 3])))

Using VSCode and when hovering mouse on integer on line async for integer in integers: it shows "(variable) integer: Unknown". It leads me wonder if this will make auto completion tools and type checkers understand AList and alist correctly. Code runs without errors.

Answer 1

list itself is generic (since Python 3.9); just use

import asyncio
from typing import Generic, TypeVar

T = TypeVar("T")


class alist(list[T]):
    async def __aiter__(self):
        for _ in self:
            yield _


async def func(integers: alist[int]):
    async for integer in integers:
        print(integer)


asyncio.run(func(alist([1, 2, 3])))

typing.List is deprecated, an artifact of a time when the built-in types could not be used generically.