abstractsignature

This package provides a method for enforcing consistent function signatures between abstractmethod implementations. This hopes to make large libraries where many classes inherit a common interface from a single abstract definition easier to maintain.

Classes which inherit an @abstractmethod with an @abstractsignature will fail to instantiate if their signature does not equal the abstraction.

Two signatures are considered equal if all their parameters are equal (excluding the implicit self/cls parameter for instance and class methods), their positional and positional only parameters are in the same order, and they have equal return annotations. Parameters are considered equal if they have the same name, kind, default value, and annotation.

Install

Install from git:

uv add git+https://github.com/d-c-gray/abstractsignature.git

Usage

Create a class that inherits from ABCSignature, and define abstract methods. Add the @abstractsignature decorator above the @abstractmethod decorator.

from abstractsignature import abstractsignature, ABCSignature
from abc import abstractmethod

class MyInterface(ABCSignature):
    @abstractsignature
    @abstractmethod
    def my_method(self, a: int) -> int:
        return a + 1

class MyImplementation(MyInterface):
    def __init__(self):
        super().__init__()
    def my_method(self, number: int) -> int:
        return number + 1

MyImplementation()

If the implemented signature doesn't match the defined signature, you will get an error:

abstractsignature.abstractsignature.IncorrectSignatureError: implementation <bound method MyImplementation.my_method of <__main__.MyImplementation object at 0x00000135A7E1EE40>> does not match abstract definition of <class '__main__.MyInterface'>:
Implemented signature:
 (number: int) -> int
Abstract signature:
 (a: int) -> int

This pattern also works with @classmethod and @staticmethod

from abstractsignature import abstractsignature, ABCSignature
from abc import abstractmethod

class MyInterface(ABCSignature):
    @classmethod
    @abstractsignature
    @abstractmethod
    def my_class_method(cls, a: int) -> int:
        return a + 1

    @staticmethod
    @abstractsignature
    @abstractmethod
    def my_static_method(cls, a: int) -> int:
        return a + 1

This project was built from simple-modern-uv.