quacks 0.1.1

Improved, mypy-compatible duck typing with Protocol

If it walks like a duck and it quacks like a duck, then it must be a duck

Improved, mypy-compatible duck typing with Protocol.

Why?

PEP544 gave us Protocol, a way to define duck typing statically. In some cases, it’s still a bit cumbersome to work with. This library gives you some much needed niceties.

Features

Easy read-only protocols

Defining read-only protocols is great for encouraging immutability and working with frozen dataclasses. Use the readonly decorator:

from quacks import readonly

@readonly
class User(Protocol):
    id: int
    name: str
    is_premium: bool

Without this decorator, we’d have to write quite a lot of cruft, reducing readability:

class User(Protocol):
    @property
    def id(self) -> int: ...
    @property
    def name(self) -> str: ...
    @property

Partial protocols (🚧 work in progress 🚧)

What if you only need part of a protocol? Imagine we have several functions who use various properties of User. With partial protocols you can reuse a data ‘shape’ without requiring all attributes.

(exact syntax TBD)

from quacks import q

def determine_discount(u: User[q.id.is_premium]) -> int:
    ...  # access `id` and `is_premium` attributes

def greet(u: User[q.id.name]) -> None:
    ...  # access `id` and `name` attributes

u: User = ...

determine_discount(u)
greet(u)