Unassigned Locker Numbers

PandasMediumMid level~10 min

Problem

A gym assigns sequentially numbered lockers to members, but some numbers in the run are currently empty. The `locker` DataFrame has `locker_no` (an assigned locker number) and `holder_name`.\n\nReturn every locker number between 1 and the largest assigned `locker_no` that is **not** currently assigned. Name the single output column `gap_no`.

Input data

Example rows — the live problem includes the full dataset.

locker

locker_no	holder_name
1	Hugo
4	Iris
5	Jonas

Expected output

Your answer should return 2 rows with the columns gap_no.

Starter code (Pandas (Python))

import pandas as pd

def unassigned_lockers(locker) -> pd.DataFrame:
    # Your code here
    return locker

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