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This question has already been discussed in #18 long time ago, but now I stumble on this in a practical question: How to annotate something that subclasses two ABC's. Currently, a workaround is to introduce a "mix" class:
from typing import Iterable, Container
class IterableContainer(Iterable[int], Container[int]):
...
def f(x: IterableContainer) -> None: ...
class Test(IterableContainer):
def __iter__(self): ...
def __contains__(self, item: int) -> bool: ...
f(Test())
but mypy complains about this
error: Argument 1 of "__contains__" incompatible with supertype "Container"
But then I have found this code snippet in #18
def assertIn(item: T, thing: Intersection[Iterable[T], Container[T]]) -> None:
if item not in thing:
# Debug output
for it in thing:
print(it)
Which is exactly what I want, and it is also much cleaner than introducing an auxiliary "mix" class. Maybe then introducing Intersection
is a good idea, @JukkaL is it easy to implement it in mypy?