dataclass-extensions 0.3.0

Additional functionality for Python dataclasses

dataclass-extensions

Additional functionality for Python dataclasses

Installation

Python 3.10 or newer is required. You can install the package from PyPI:

pip install dataclass-extensions

Features

Encode/decode to/from JSON-safe dictionaries

from dataclasses import dataclass
from dataclass_extensions import decode, encode


@dataclass
class Fruit:
    calories: int
    price: float

@dataclass
class FruitBasket:
    fruit: Fruit
    count: int

basket = FruitBasket(fruit=Fruit(calories=200, price=1.0), count=2)
assert encode(basket) == {"fruit": {"calories": 200, "price": 1.0}, "count": 2}
assert decode(FruitBasket, encode(basket)) == basket

You can also define how to encode/decode non-dataclass types:

from dataclasses import dataclass
from dataclass_extensions import decode, encode


class Foo:
    def __init__(self, x: int):
        self.x = x

@dataclass
class Bar:
    foo: Foo

encode.register_encoder(lambda foo: {"x": foo.x}, Foo)
decode.register_decoder(lambda d: Foo(d["x"]), Foo)

bar = Bar(foo=Foo(10))
assert encode(bar) == {"foo": {"x": 10}}
assert decode(Bar, encode(bar)) == bar

Polymorphism through registrable subclasses

from dataclasses import dataclass
from dataclass_extensions import Registrable, decode, encode


@dataclass
class Fruit(Registrable):
    calories: int
    price: float

@Fruit.register("banana")
@dataclass
class Banana(Fruit):
    calories: int = 200
    price: float = 1.25

@Fruit.register("apple")
@dataclass
class Apple(Fruit):
    calories: int = 150
    price: float = 1.50
    variety: str = "Granny Smith"

@dataclass
class FruitBasket:
    fruit: Fruit
    count: int

basket = FruitBasket(fruit=Apple(), count=2)
assert encode(basket) == {
    "fruit": {
        "type": "apple",  # corresponds to the registered name
        "calories": 150,
        "price": 1.5,
        "variety": "Granny Smith",
    },
    "count": 2,
}
assert decode(FruitBasket, encode(basket)) == basket