How to typehint an instance of a class that is going to implement multiple Protocols in a context?

[FeryET]

I have also asked this question here.

I have an object inside a context I want to use from both it's superclass methods, and given the function, use of its multiple protocol methods it has implemented. How can I typehint it in a way so mypy understands that?

[srittau]

@FeryET Could you give an example so it's easier to understand what you mean?

[Gobot1234]

Looking at the stack overflow post you should just use the Father type hint as that's how duck typing works, Father quacks like DummyProtocol as it defines do_something. If that's not what you mean, I need another example.

[Gobot1234]

Not currently no but there is a PEP for it, which is why I gave the second option of creating another protocol with all of the methods required

[a-reich]

Or you can create a new protocol class that just inherits from each of the previous protocols, right?

class ProtoIntersection(ProtocolA, ProtocolB, ProtocolC, typing.Protocol): …

[Gobot1234]

Yes

[FeryET]

Or you can create a new protocol class that just inherits from each of the previous protocols, right?

class ProtoIntersection(ProtocolA, ProtocolB, ProtocolC, typing.Protocol): …

That is a bit inconvenient tho, especially for something that is only used for static typing like Protocols. It reduces readability and transparency.

[Gobot1234]

Yes this is one of the proposed use cases for an intersection as you could just do ProtocolA & ProtocolB & ProtocolC