protocol-design

Python typing.Protocol enables structural subtyping for interface design by allowing you to define contracts between modules using duck typing without requiring shared inheritance hierarchies.

Python Protocol uses structural subtyping to define interfaces without forcing inheritance, whereas Abstract Base Classes (ABCs) require explicit inheritance to enforce interface contracts across components.

@runtime_checkable allows runtime instance checks for Python Protocol implementations, but it only verifies method presence and not their type signatures, presenting notable limitations for robust validation.

Yes, you can use Mock(spec=Protocol) in Python to ensure type-safe testing, allowing your test suites to accurately mock structural subtyping interfaces without explicit inheritance.

You can compose multiple Python Protocols by combining them, creating a single unified interface that enforces the combined structural subtyping contracts across your application components.

You should avoid Python typing.Protocol when you need strict nominal subtyping or runtime method signature validation, as Protocol primarily supports structural duck typing without deep signature enforcement.