Was the Second Supply a Preferred Vendor?

PandasHardSenior level~10 min

Problem

You are given three DataFrames. `contractors` (from `contractors.csv`) has `contractor_id` (the key), `onboarded_day` and `preferred_vendor`. `supplies` (from `supplies.csv`) has `supply_id` (the key), `supplied_day`, `material_id` and `contractor_id` — the contractor who supplied the material (assume each contractor's supply dates are distinct). `materials` (from `materials.csv`) has `material_id` (the key) and `vendor`.

For each contractor, determine whether the **vendor of the second material they supplied (ordered by supply date)** equals their `preferred_vendor`. If the contractor supplied fewer than two materials, report `'no'`. Return `contractor_id` and a column named `second_supply_preferred` holding `'yes'` or `'no'`.

Example: contractor 1 prefers Acme; their second supply (material 200) is from Acme -> yes. Contractor 2 prefers Globex but supplied only one material -> no.

Input data

Example rows — the live problem includes the full dataset.

contractors

contractor_id	onboarded_day	preferred_vendor
1	2023-01-01	Acme
2	2023-01-01	Globex

supplies

supply_id	supplied_day	material_id	contractor_id
10	2023-02-01	100	1
11	2023-02-05	200	1
12	2023-03-01	300	2

materials

material_id	vendor
100	Globex
200	Acme
300	Globex

Expected output

Your answer should return 2 rows with the columns contractor_id, second_supply_preferred.

Starter code (Pandas (Python))

import pandas as pd

def second_supply_check(contractors, supplies, materials) -> pd.DataFrame:
    # Your code here
    return contractors

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