フリー問題

問題文

A dataframe has a category column and a numeric amount column. Which pair of operations produces the total amount for each category?

選択肢

1. Set the category column as the index and call the summary-statistics method, so the totals arrive as one of its rows.
2. Sort the dataframe by the category column and then take a cumulative sum of the amount column, because sorting places identical categories next to each other and the running total then gives the per-category figure directly.
3. Group the dataframe by the category column and then apply a sum aggregation to the amount column.
4. Filter the dataframe once per category and sum each result, so the full table is scanned once for every category present.