Omid - Challenge 117

data-challenges
advanced-exercises
🔰 Challenge 117: Add Index Column!
Published

March 24, 2026

Illustration for Omid - Challenge 117

Challenge Description

🔰 Challenge 117: Add Index Column!

Solutions

library(tidyverse)
library(readxl)

path = "files/CH-117 Add Index Column.xlsx"
input = read_excel(path, range = "B2:C13")
test  = read_excel(path, range = "E2:G13")

result = input %>%
  mutate(index = row_number(), .by = Stock)

all.equal(result, test)
#> [1] TRUE

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Builds the intermediate columns that drive the final result

  • Strengths:

    • The R solution stays close to the workbook rule and keeps the transformation compact.

  • Areas for Improvement:

    • The code assumes the sheet structure and source ranges remain stable.

  • Gem:

    • The strongest part of the solution is choosing the right intermediate representation before shaping the final output.
import pandas as pd

path = "CH-117 Add Index Column.xlsx"
input = pd.read_excel(path, usecols="B:C", skiprows=1)
test = pd.read_excel(path, usecols="E:G", skiprows=1).rename(columns=lambda x: x.replace(".1", ""))

result = input.assign(index = input.groupby("Stock").cumcount() + 1)
print(result.equals(test))  # True

  • Logic:

    • Reads the workbook ranges needed for the challenge

    • Aggregates or ranks values at the relevant grouping level

    • Builds the intermediate columns that drive the final result

  • Strengths:

    • The Python version follows the same rule in a direct dataframe-oriented implementation.

  • Areas for Improvement:

    • The code assumes the workbook layout remains stable, so any sheet redesign would require small adjustments.

  • Gem:

    • The implementation stays close to the original workbook rule instead of adding unnecessary abstraction.

Difficulty Level

This task is moderate:

  • The business rule is readable, but the workbook still requires careful implementation to reach the expected layout.