Unique values, order preserved

pythoneasysetslists

Write dedupe(items) that returns a new list with duplicates removed while keeping the first-seen order.

hint ladder

sql ↔ pandas

solution.py

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Reference solution

The shape we check against. Any implementation that passes the assertions is valid — this one favours clarity.

def dedupe(items):
    seen = set()
    out = []
    for x in items:
        if x not in seen:
            seen.add(x)
            out.append(x)
    return out

Code is blurred until you solve this problem — the reasoning stays readable.