Trial Users Who Became Buyers

PandasHardSenior level~10 min

Problem

You are given a DataFrame `activity` with columns `user_ref`, `acted_at`, `action_id`, and `action_type`, where `action_type` is either `Trial` or `Purchase`.

For users whose **very first action** (earliest `acted_at`) was a `Trial`, count how many `Purchase` actions they later performed. Output `user_ref` and `purchase_count`, ordered by `purchase_count` descending and then `user_ref` descending.

Input data

Example rows — the live problem includes the full dataset.

activity

user_ref	acted_at	action_id	action_type
11	2024-01-01 09:00:00	1	Trial
11	2024-01-05 09:00:00	2	Purchase
11	2024-01-08 09:00:00	3	Purchase
12	2024-01-02 10:00:00	4	Purchase
12	2024-01-09 10:00:00	5	Purchase

Expected output

Your answer should return 2 rows with the columns user_ref, purchase_count.

Starter code (Pandas (Python))

import pandas as pd

def trial_users_who_became_buyers(activity) -> pd.DataFrame:
    # Your code here
    return activity

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