Traitor

A small experiment in trait-like composition using Python’s Protocol, inspired by Rust's traits (while being a lot less powerful — and arguably less useful).

I never said it was a good idea! Implemented just for fun.

---

How to try it out

This project uses uv out of habit (ok, it's overkill here...)

uv venv
source .venv/bin/activate
uv pip install -e .

Then run the example:

python example.py

What is this?

Traitor is a tiny Python library inspired by Rust's traits, built on top of Python's Protocol.

It lets you:

• Declare traits using @trait (a thin @runtime_checkable wrapper)
• Mark classes as implementing traits with @impl(...)
• Enforce trait conformance at runtime via a base class (Traitor)
• Compose behavior in a declarative way

Example:

from traitor import trait, impl, Traitor
from typing import Protocol

@trait
class Loggable(Protocol):
    def log(self) -> None: ...

@impl(Loggable)
class MyClass(Traitor):
    def log(self): print("hello")

MyClass().if_implements(Loggable).log()  # prints "hello"

---

Why the name?

Because it betrays Rust traits just as much as Python inheritance.