Unpivot Sensor Readings Into Tall Format

PandasHardSenior level~10 min

Problem

An IoT platform stores readings in a wide format. The DataFrame `readings` (loaded from `readings.csv`) has one row per device with columns `device_id`, `Alpha`, `Bravo`, `Delta`, `Echo`, where each non-id column is the reading that device produced at the gauge of that name, or NaN if there is no reading there.

Reshape the data into a tall format with exactly three columns: `device_id`, `gauge`, and `value`. Produce one row per (device, gauge) where a reading actually exists; skip any combination whose value is missing.

Return the result in any order.

Input data

Example rows — the live problem includes the full dataset.

readings

device_id	Alpha	Bravo	Delta	Echo
1	12		40
2		7		55
3	9	8	3	2

Expected output

Your answer should return 8 rows with the columns device_id, gauge, value.

Starter code (Pandas (Python))

import pandas as pd

def unpivot_sensor_readings(readings) -> pd.DataFrame:
    # Your code here
    return readings

Solve this Pandas question free

Write Pandas (Python) and run it instantly in your browser — even on your phone. No signup needed to try.

Solve it now → Create free account

Solution & explanation

Create a free account to unlock the optimal solution, a step-by-step explanation, and the hidden test cases that grade your answer.