Protocol

July 13, 2024

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A protocol is a way to define structural typing or "duck typing" in Python. It defines a set of attributes and/or methods that an object must have in order to be considered compatible with that protocol. Below is a protocol defined as an Activity class which must have name and duration attributes along with a get_message method.

from typing import Protocol

class Activity(Protocol):
    name: str
    duration: int

    def get_message(self, x: str) -> str: ...

Below is a ShellActivity class that conforms to the Activity protocol because it has name and duration attributes and a get_message method.

class ShellActivity:
    name: str
    age: int
    duration: int

    def get_message(self, x: str):
        return f"hello {x}"

# Create an instance of a ShellActivity object
shell: Activity = ShellActivity()