Validate dataclass fields with __post_init__ in Python

from dataclasses import dataclass, field
from typing import Optional


@dataclass
class Product:
    name: str
    price: float
    quantity: int = 1
    category: Optional[str] = None

    def __post_init__(self):
        if not self.name or not isinstance(self.name, str):
            raise ValueError("name must be a non-empty string")
        if self.price < 0:
            raise ValueError("price must be non-negative")
        if not isinstance(self.price, (int, float)):
            raise TypeError("price must be numeric")
        if self.quantity <= 0:
            raise ValueError("quantity must be positive")
        if not isinstance(self.quantity, int):
            raise TypeError("quantity must be integer")
        if self.category is not None and not isinstance(self.category, str):
            raise TypeError("category must be a string or None")


if __name__ == "__main__":
    # Valid product
    product = Product(name="Laptop", price=999.99, quantity=2, category="electronics")
    print(product)

    # Invalid attempts
    for invalid in [
        dict(name="", price=10.5),
        dict(name="Phone", price=-5),
        dict(name="Phone", price=5, quantity=0),
        dict(name=123, price=5),
        dict(name="Phone", price=10, category=99),
    ]:
        try:
            Product(**invalid)
        except (ValueError, TypeError) as e:
            print(f"Invalid: {invalid} -> {type(e).__name__}: {e}")