How to restrict a generic class to a Protocol?

[jugaadi]

from typing import Protocol

class A(Protocol):
    def x(): ...
    def y(): ...

class B:
    def __getattr__(self, name) -> Callable:
    

b = B()
b.x()
b.y()
b.z()  # error

Is there any way to limit B from accepting attributes not compatible with A protocol?

[erictraut]

Can you provide more details? What do you mean by "restrict B"? Also, A is not currently defined as a protocol in your example, Did you intend for A to be a subclass of Protocol?

[jugaadi]

@erictraut

Sorry.. Ive updated the message with the corrections and an example. Since any method can be called via B, I wanted to know whether we can constrain the attributes that can be called from B by associating it with A.

To achieve the same result, Im currently using the below solution:

def __getattr__(self, name: Literal['x', 'y']):

[erictraut]

If you want to ensure that B provides the methods required for protocol A, I recommend not supplying a __getattr__ method and instead defining individual methods x and y within B. If B subclasses from A, type checkers will validate it defines all required methods for A.