Core Collections · interview question

A bug appears around sorting and grouping. What is the strongest first debugging move?

Multiple choiceMediumchapter-3-curatedpremiumcore-collectionssorting-and-grouping

python

lines = [{"sku": "SKU-2", "qty": 1}, {"sku": "SKU-1", "qty": 4}]
lines.sort(key=lambda row: row["sku"])
print(lines)

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

Answer and explanation

Correct answer

A. 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. Performing extra sorting or grouping without a reason adds cost and cognitive noise.

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A bug appears around sorting and grouping. What is the strongest first debugging move?

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