Time: 0:00
Test a custom input to verify an edge case (e.g. empty lists, negative numbers, duplicates).
This bug belongs to the logic errors pattern
The wrong operator, an inverted condition, a formula the right way round but backwards.
What went wrong: dict.copy() creates a shallow copy. Nested dictionaries are still shared by reference, so mutating cfg['db']['port'] mutates default_config.
The fix: Use copy.deepcopy() to clone all nested levels: cfg = copy.deepcopy(default_config)
Remember: In Python, dict.copy() is shallow; use copy.deepcopy() when modifying nested mutable objects.
The pattern behind it: logic errors.
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<iframe src="https://trybughunt.com/embed/ebe81439-aaa3-46dc-9746-480a8926b476" title="Debugging challenge: Shallow dictionary copy mutates original nested port in place" width="100%" height="580" loading="lazy" style="border:1px solid #d4d4d8;border-radius:12px;max-width:760px"></iframe>
<p style="font-size:14px">Debugging challenge from <a href="https://trybughunt.com/challenges/ebe81439-aaa3-46dc-9746-480a8926b476">TryBugHunt</a></p>