Python Protocols Bring Static Type Safety to Duck Typing

A tutorial published on DEV Community explains how Python's Protocol class, available via the typing module, enables structural subtyping — often called static duck typing. Unlike traditional duck typing, Protocols allow developers to define expected method and attribute contracts that static type checkers like mypy can verify before code is executed. Classes satisfy a Protocol simply by implementing the required methods or attributes, with no inheritance or shared base class needed. The article demonstrates practical use cases such as unifying unrelated data-source classes under a single Readable protocol. Protocols are recommended when writing flexible, type-safe code, though runtime enforcement requires the optional @runtime_checkable decorator.