How Often Each Host Was a Guest

PandasMediumMid level~10 min

Problem

You are given one DataFrame `episodes` with columns `episode_id`, `host_id`, and `guest_id`. `episode_id` is unique; `host_id` is the person running the episode and `guest_id` is the person invited onto it.

For each distinct person who has hosted at least one episode, return their id as `host_id` and `appearances`: the number of episodes in which that person appeared as a guest (0 if they were never a guest).

Return the result in any order.

Input data

Example rows — the live problem includes the full dataset.

episodes

episode_id	host_id	guest_id
1	10	20
2	10	30
3	20	10
4	30	10
5	20	40

Expected output

Your answer should return 3 rows with the columns host_id, appearances.

Starter code (Pandas (Python))

import pandas as pd

def host_guest_appearances(episodes) -> pd.DataFrame:
    # Your code here
    return episodes

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Solution & explanation

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