Top Three Sellers per Warehouse

PandasHardSenior level~10 min

Problem

A retailer ranks products by units sold within each warehouse.

DataFrame: `products` (from `products.csv`)

| Column | Type |
|---------------|---------|
| product_id | int |
| product_name | object |
| units_sold | int |
| warehouse_id | int |

DataFrame: `warehouses` (from `warehouses.csv`)

| Column | Type |
|----------------|--------|
| warehouse_id | int |
| warehouse_name | object |

A product is a **best seller** in its warehouse if its `units_sold` is among the **top three distinct** unit-sold values for that warehouse. Several products may share a unit-sold value, and a tied value counts as one of the three distinct levels (use a dense rank).

Write a function that returns the best sellers as three columns named `warehouse`, `product`, and `units`, in any order.

Input data

Example rows — the live problem includes the full dataset.

products

product_id	product_name	units_sold	warehouse_id
1	Stapler	85	1
2	Lamp	80	2
3	Mug	60	2
4	Chair	90	1
5	Pen Set	69	1

warehouses

warehouse_id	warehouse_name
1	North
2	South

Expected output

Your answer should return 6 rows with the columns warehouse, product, units.

Starter code (Pandas (Python))

import pandas as pd

def best_sellers(products: pd.DataFrame, warehouses: pd.DataFrame) -> pd.DataFrame:
    # Your code here
    return products

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