Amazon Unique Shipments per Month

PandasMediumMid levelAmazon~15 min

Problem

**[Asked at Amazon]**

Some shipments are logged multiple times. Deduplicate on the composite key
`(product_id, warehouse_id, ship_date)`, then count **unique shipments per
month**.

Return `month` (YYYY-MM) and `unique_shipments`, ordered by month.

Input data

Example rows — the live problem includes the full dataset.

shipments

shipment_id	product_id	warehouse_id	ship_date
1	100	W1	2023-01-15
2	101	W1	2023-01-20
3	100	W1	2023-01-15
4	102	W2	2023-02-10
5	100	W1	2023-02-25

Expected output

Your answer should return 2 rows with the columns month, unique_shipments.

Starter code (Pandas (Python))

import pandas as pd

def shipments_per_month(shipments: pd.DataFrame) -> pd.DataFrame:
    # Your code here
    return shipments

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