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Remove Duplicates, Keep the Order

Beginner · Write the code · from 50 Python Practice Problems with Instant Answer Checking (Beginner to Advanced)

From the lesson: 50 Python Practice Problems with Instant Answer Checking (Beginner to Advanced)

Fifty problems, each with a code editor and real tests. Write your solution, press Check, and see exactly which cases pass. Stuck? Hints reveal one at a time, and the solution unlocks once you have checked at least once. Your code and progress are saved in this browser.

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Write dedupe(items) that returns a new list without duplicates, keeping the first occurrence of each item in its original position.

dedupe([3, 1, 3, 2, 1])  ->  [3, 1, 2]
def dedupe(items):
pass
Solution unlocks after your first Check

What Check runs

Your code runs first, then each of these lines. The output must match exactly.

RunsExpected output
dedupe([3, 1, 3, 2, 1])[3, 1, 2]
dedupe(["b", "a", "b"])['b', 'a']

More practice problems

All Python exercises · 50 practice problems