Class 数据类中的属性和元类

Question

我有一些 Python class 具有 class 属性和元 class:

from abc import ABCMeta

class OldProduct(metaclass=ABCMeta):
    c_type: str
    c_brand: str

    def __init__(self, name:str):
        self.name = name

class OldLegoBox(OldProduct):
    c_type = "Toy"
    c_brand = "Lego"

    def __init__(self, name:str, price:float):
        self.name = name
        self.price = price

oldbox1 = OldLegoBox("Princess", 12.3)
print(oldbox1.c_brand)
oldbox2 = OldLegoBox("Knight", 42.3)
print(oldbox2.c_brand)

我想用dataclasses改进代码：如何处理class属性c_type和c_brand?

我正在考虑以下似乎满足我需要的东西：

from abc import ABCMeta
from dataclasses import dataclass, field


@dataclass
class Product(metaclass=ABCMeta):
    c_type: str
    c_brand: str
    name: str


@dataclass
class LegoBox(Product):
    name: str
    price: float
    c_type: str = field(default="Toy", init=False)
    c_brand: str = field(default="Lego", init=False)


box1 = LegoBox("Princess", 12.3)
print(box1)
box1.price = 1000
box1.name = "toto"
box1.c_brand = "some brand"
print(box1)
box2 = LegoBox("Knight", 42.3)
print(box2)

有没有更合适的做法？

Answer 1

Dataclass class variables should be annotated with typing.ClassVar

@dataclass
class Product(metaclass=ABCMeta):
    c_type: ClassVar[str]
    c_brand: ClassVar[str]
    name: str

@dataclass
class LegoBox(Product):
    c_type: ClassVar[str] = "Toy"
    c_brand: ClassVar[str] = "Lego"
    price: float

据我所知，使用抽象类实际上不会给您带来任何好处，因为没有抽象方法。您仍然可以创建 Product 的实例，但它们将没有 c_type 或 c_brand 属性。

Class 数据类中的属性和元类

Class Attribute and metaclass in dataclasses

python

python-dataclasses