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Domain Modeling · interview question

What is the healthiest performance judgment around invariants in __post_init__?

Multiple choiceMediumchapter-7-curatedpremiumdomain-modelinginvariants-in-post-init
python
from dataclasses import dataclass

@dataclass
class OrderLine:
    sku: str
    quantity: int

    def __post_init__(self) -> None:
        if self.quantity <= 0:
            raise ValueError("quantity must be positive")
Choose one answer
Answer and explanation

Correct answer

D. Measure before optimizing, then change the part that actually dominates cost instead of guessing from style alone.

Why

Premature optimization is usually weaker than targeted optimization backed by measurement.

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