Group totals: SUMIF and pivot tables
Spreadsheet SUMIF adds values whose category matches. groupby does this for every category at once:
totals = sales.groupby("region", as_index=False)["amount"].sum()
The result has one row per region. as_index=False keeps the group label in a normal column. sum() totals amounts; count() counts nonmissing values in the selected column; mean() averages them. Choose the operation that answers the business question.
Group by two categories with work.groupby(["team", "kind"], as_index=False)["minutes"].sum(). Each distinct team/kind pair gets its own total.
totals = totals.sort_values("region").reset_index(drop=True) sorts the region labels alphabetically and gives the result a fresh row index. For a team/kind summary, pass ["team", "kind"] to sort_values to sort by team first, then kind within each team. Store the returned table; these calls do not change the original.
A pivot table lays out two categories like a spreadsheet pivot:
grid = sales.pivot_table(index="region", columns="channel", values="amount", aggfunc="sum", fill_value=0)
aggfunc="sum" matters: pivot_table defaults to an average. fill_value=0 means a category combination with no sales displays as zero. A pivot's row labels form its index: grid = grid.sort_index().sort_index(axis=1) sorts row labels, then column labels (axis=1). sort_values instead sorts rows using values in named columns.
See it run
import pandas as pd spend = pd.DataFrame({"dept": ["ops", "hr", "ops", "hr", "it"], "cost": [10, 5, 20, 7, 3]}) by_dept = spend.groupby("dept")["cost"].sum() flat = by_dept.reset_index()
groupby = split rows into piles by a key, then summarise each pile.
Practice group totals: sumif and pivot tables
Exercise 1
An office manager needs spending totals by department, like SUMIF in a budget sheet. Read team_spend.csv as spend. Create totals with columns department and amount, summed by department and sorted alphabetically by department with a fresh row index.
Exercise 2
A warehouse planner wants a shipping pivot. Load channel_units.csv as sales. Build grid with region as rows, channel as columns, and summed units as cells. Show zero for absent combinations. Sort both axes alphabetically.
Exercise 3
A service supervisor budgets time by team and work type. Read service_minutes.csv as work. Produce totals with team, kind, minutes: sum minutes for each team/kind pair, sort by team then kind alphabetically, and reset the row index. Do not combine a team's installation and repair budgets.
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Practice
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