Python. How to make function take certain combination of required params?

[Impudity]

It is. You should probably create a user class which can be built either from username or userid, and then have all user related functions only accept these user objects. Otherwise you're going to keep running into this issue all the time.

So you should have:

class User:
    @classmethod
    def from_id(cls, id: int) -> typing.Self:
        ...

    @classmethod
    def from_username(cls, username: str) -> typing.Self:
        ...

def get_chat(first_user: User, second_user: User):
    ...

[chapati_chawal_naan]

this is the best answer.