Python Data Classes Tutorial

# Python Data Classes Tutorial Python data classes, introduced in Python 3.7, provide a decorator for automatically generating special methods for classes that primarily store data. ## Basic Data Class ```python from dataclasses import dataclass @dataclass class User: name: str email: str age: int active: bool = True user = User("Alice", "alice@example.com", 30) print(user) # User(name='Alice', email='alice@example.com', age=30, active=True) ``` ## Auto-Generated Methods Data classes automatically generate: - `__init__()` - `__repr__()` - `__eq__()` ## Immutable Data Classes ```python @dataclass(frozen=True) class Point: x: float y: float p = Point(1.0, 2.0) # p.x = 3.0 # Raises FrozenInstanceError ``` ## Default Values and Factories ```python from dataclasses import dataclass, field from typing import List @dataclass class ShoppingCart: items: List[str] = field(default_factory=list) total: float = 0.0 def add_item(self, item: str, price: float): self.items.append(item) self.total += price ``` ## Comparison and Ordering ```python @dataclass(order=True) class Product: name: str = field(compare=False) price: float p1 = Product("Widget", 10.0) p2 = Product("Gadget", 15.0) print(p1 < p2) # True ``` ## Post-Init Processing ```python @dataclass class Rectangle: width: float height: float area: float = field(init=False) def __post_init__(self): self.area = self.width * self.height ``` ## When to Use Data Classes - Classes that primarily store data - Want automatic method generation - Need immutability (frozen=True) - Value objects in domain models Data classes reduce boilerplate and make your code more maintainable. Use them whenever appropriate!