TIL - Protocol Classes Enable Structural Typing (Duck Typing with Type Safety)

Today I Learned Apr 24, 2026

typing.Protocol lets you define an interface based on structure, not inheritance. Any class that has the required methods satisfies the protocol - no explicit implements needed.

from typing import Protocol


class Drawable(Protocol):
    def draw(self) -> None: ...


class Circle:
    def draw(self) -> None:
        print("Drawing circle")


def render(shape: Drawable) -> None:
    shape.draw()


render(Circle())  # no inheritance required