**Ordered Dedup:** dict.fromkeys(lst) (Py 3.7+) or seen=set(); [x for x in lst if not (x in seen or seen.add(x))]. O(n), hashable elements. **Unhashable:** O(n²) with list+in, or convert to tuple for hashable key....
This easy-level Python/Coding question appears frequently in data engineering interviews at companies like Nielsen. While less common, it tests deeper understanding that distinguishes strong candidates. Mastering the underlying concepts (python) will help you answer variations of this question confidently.
Start by clearly defining the core concept being asked about. Interviewers want to see that you understand the fundamentals before diving into implementation details. Structure your answer with a definition, then explain the practical application with a concise example.
Ordered Dedup: dict.fromkeys(lst) (Py 3.7+) or seen=set(); [x for x in lst if not (x in seen or seen.add(x))]. O(n), hashable elements.
Unhashable: O(n²) with list+in, or convert to tuple for hashable key. For DataFrames: drop_duplicates(subset=['key_col']).
def dedupe(lst):
return list(dict.fromkeys(lst))
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Analyze My Answer — FreeAccording to DataEngPrep.tech, this is one of the most frequently asked Python/Coding interview questions, reported at 1 company. DataEngPrep.tech maintains a curated database of 1,863+ real data engineering interview questions across 7 categories, verified by industry professionals.