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Python Dataclasses

OOP Modern Tools

Dataclasses

`@dataclass` reduces boilerplate for classes that primarily store data.

Define dataclassesImmutability & slots

Definition​

from dataclasses import dataclass, field
from datetime import datetime, timezone

@dataclass
class Invoice:
    total: float
    customer: str
    created_at: datetime = field(default_factory=lambda: datetime.now(timezone.utc))
  • Generates __init__, __repr__, __eq__ automatically.
  • Use field(default_factory=...) for mutable defaults.

Advanced options​

  • frozen=True -> immutable instances.
  • slots=True (Python 3.10+) -> reduces memory usage.
  • kw_only=True -> keyword-only init parameters.

Post-init processing​

Use __post_init__ for validation or derived fields:

@dataclass
class Order:
    quantity: int
    unit_price: float
    total: float = field(init=False)

    def __post_init__(self):
        if self.quantity <= 0:
            raise ValueError("quantity must be positive")
        self.total = self.quantity * self.unit_price

Next up in your learning path

Slots

Optimize attribute storage even without dataclasses.

Performance

Abstract classes

Combine dataclasses with ABCs for structure + data.

Architecture

Type hints

Document dataclass fields for static analysis.

Reference