Are there any alternative to this overload case in python with typing?

Question

currently I am implementing a lot of subclasses that should implement a function, this is a minimal example of the current project.

In this case, I have a function that needs to call, to the login of a user, but depending of the implementation injected previously the application will use UserUP or UserToken

Because in login_user I have all data available for the two options, I set the params like follow.

from typing import Protocol, runtime_checkable

@runtime_checkable
class User(Protocol):
    def login(self, **kwargs) -> None:
        raise NotImplementedError


class UserUP(User):
    def login(self, user: str, password:str, **kwargs) -> None:
        print(user)
        print(password)


class UserToken(User):
    def login(self, token:str, **kwargs) -> None:
        print(token)


def login_user(user: User) -> None:
    user.login(user="user", password="password", token="Token")

login_user(UserUP())
login_user(UserToken())

The problem is that when I run mypy I get errors like the following:

app.py:10: error: Signature of "login" incompatible with supertype "User"  [override]
app.py:10: note:      Superclass:
app.py:10: note:          def login(self, **kwargs: Any) -> None
app.py:10: note:      Subclass:
app.py:10: note:          def login(self, user: str, password: str, **kwargs: Any) -> None
app.py:16: error: Signature of "login" incompatible with supertype "User"  [override]
app.py:16: note:      Superclass:
app.py:16: note:          def login(self, **kwargs: Any) -> None
app.py:16: note:      Subclass:
app.py:16: note:          def login(self, token: str, **kwargs: Any) -> None

Of course, the signature is incompatible, but which alternatives do I have to implement things like this?

Asked By: Tlaloc-ES

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Source

Answer 1

Use keyword_only marker in all signatures and describe all possible parameter in `User.login`

You need to expose which possible keywords can be used, and which type, in the main function.

from typing import Protocol, runtime_checkable


@runtime_checkable
class User(Protocol):
    def login(self, *, user: str, password: str, token: str, **kwargs) -> None:
        raise NotImplementedError


class UserUP(User):
    def login(self, *, user: str, password: str, **kwargs) -> None:
        print(user)
        print(password)


class UserToken(User):
    def login(self, *, token: str, **kwargs) -> None:
        print(token)


def login_user(user: User) -> None:
    user.login(user="user", password="password", token="Token")


login_user(UserUP())
login_user(UserToken())

Success: no issues found in 1 source file

Answered By: Dorian Turba

Are there any alternative to this overload case in python with typing?

Question:

Answers:

Use keyword_only marker in all signatures and describe all possible parameter in `User.login`

Are there any alternative to this overload case in python with typing?

Question:

Answers:

Use keyword_only marker in all signatures and describe all possible parameter in User.login

Use keyword_only marker in all signatures and describe all possible parameter in `User.login`