YouTip

What are Data Classes?

Data classes (Python 3.7+) reduce boilerplate for classes that primarily store data. They auto-generate __init__, __repr__, __eq__, and more.

Basic Data Class

from dataclasses import dataclass

@dataclass
class Point:
    x: float
    y: float

p = Point(3.0, 4.0)
print(p)           # Point(x=3.0, y=4.0)
print(p == Point(3.0, 4.0))  # True

With Methods

@dataclass
class Rectangle:
    width: float
    height: float

    def area(self) -> float:
        return self.width * self.height

rect = Rectangle(10, 5)
print(rect.area())  # 50

Immutable

@dataclass(frozen=True)
class Color:
    r: int
    g: int
    b: int

red = Color(255, 0, 0)
# red.r = 100  # Error!

Summary

• @dataclass auto-generates __init__, __repr__, __eq__
• Use frozen=True for immutable objects
• field() provides default_factory and other options