Description

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Advanced · 14 min

Type hints and protocols

Describe interfaces that different objects can satisfy.

Annotate intent

Type hints document expected inputs and outputs. Python still executes the function normally at runtime.

def total(values: list[int]) -> int:
    return sum(values)

print(total([2, 4, 6]))

Output

12

Describe shared behavior

A Protocol names the methods an object should provide. Unrelated classes can satisfy it without inheritance.

from typing import Protocol

class Named(Protocol):
    def name(self) -> str: ...

class User:
    def name(self) -> str:
        return "Ada"

def label(item: Named) -> str:
    return item.name().upper()

print(label(User()))

Output

ADA

Type hints and protocols

  1. Read both type hints and protocols examples before answering.
  2. Run the task, compare its exact output, and revise the code if needed.

Try it yourself

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Use a common interface

Add a title method to Article so it satisfies Titled. Keep the display call and output Python Tips.

Practice