Lookup Reservoir Levels

PandasEasyJunior level~10 min

Problem

A water authority stores the recorded level of each reservoir at the end of selected years. Analysts submit lookup requests for a reservoir in a given year; if no level was recorded for that reservoir-year, the answer is `0`.

DataFrame `readings` (from `readings.csv`) has columns `reservoir_id`, `year`, `level_cm` — the recorded end-of-year level in cm for a reservoir.

DataFrame `lookups` (from `lookups.csv`) has columns `reservoir_id`, `year` — one request per row.

For every lookup, return `reservoir_id`, `year`, and `level_cm`. If the reservoir-year is missing from `readings`, report its level as `0`. Rows may be returned in any order.

Input data

Example rows — the live problem includes the full dataset.

readings

reservoir_id	year	level_cm
1	2018	100
7	2020	30
13	2019	40
1	2019	113
2	2008	121

lookups

reservoir_id	year
1	2019
2	2008
3	2009
7	2018
7	2019

Expected output

Your answer should return 7 rows with the columns reservoir_id, year, level_cm.

Starter code (Pandas (Python))

import pandas as pd

def resolve_lookups(readings, lookups) -> pd.DataFrame:
    # Your code here
    return readings

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