Type Hints · interview question

A bug appears around optional and collections. What is the strongest first debugging move?

Multiple choiceEasychapter-10-curatedpremiumtype-hintsoptional-and-collections

python

from typing import Optional

def normalize_coupon(code: Optional[str]) -> str:
    return code or ""

Delay clarity until production traffic reveals the edge case and then patch it under pressure.Keep optional and collections implicit so the script stays short and hope the next engineer infers the rule.Solve the symptom with comments only and avoid changing the code shape around optional and collections.Trace one concrete example, inspect the state transitions, and compare them to the intended rule before rewriting anything.

Answer and explanation

Correct answer

D. Trace one concrete example, inspect the state transitions, and compare them to the intended rule before rewriting anything.

Why

That approach is reliable because it creates evidence. If None and collection contents are left implicit, edge cases spread across many call sites.

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A bug appears around optional and collections. What is the strongest first debugging move?

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