How to type hint a return value of Exception's subclass?

Question

I have an abstract method in my base class, and I want all the subclasses to return an iterable of their expected Exception classes:

class Foo(metaclass=ABCMeta):
    @abstractmethod
    def expected_exceptions(self):
        raise NotImplementedError()

class Bar(Foo):
    def expected_exceptions(self):
        return ValueError, IndexError

class Baz(Foo):
    def expected_exceptions(self):
        yield from self.manager._get_exceptions()

How do I type hint this return value? At first I thought of -> Iterable[Exception], but that would mean they are instances of Exception, as opposed to subclasses.

Asked By: Markus Meskanen

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Source

Answer 1

You want typing.Type, which specifies that you are returning a type, as opposed to an instance:

from typing import Type, Iterable

def expected_exceptions(self) -> Iterable[Type[Exception]]:
    return ValueError, IndexError

Answered By: gmds

How to type hint a return value of Exception's subclass?

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