Dataclasses

When the class is just data

Writing __init__, __repr__ and __eq__ by hand for a class that only holds values is tedious. @dataclass writes them for you:

from dataclasses import dataclass

@dataclass
class Point:
    x: int
    y: int

p = Point(1, 2)
print(p)              # Point(x=1, y=2)
Point(1, 2) == Point(1, 2)    # True

The x: int lines are annotations. Python does not enforce them — passing a string still works — but the decorator uses them to know which fields exist, and they document your intent.

Fields can have defaults, and a dataclass can still have ordinary methods:

@dataclass
class Product:
    name: str
    price: float
    quantity: int = 1

    def total(self):
        return self.price * self.quantity

Your turn: write that Product dataclass, with a total() method and a discounted(percent) method returning the total with that percentage taken off, rounded to two decimal places.