How do I create a pivot table with percentages in Pandas?

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You can use the following syntax to add a column to a pivot table in pandas that shows the percentage of the total for a specific column: 

my_table['% points'] = (my_table['points']/my_table['points'].sum())*100

This particular syntax adds a new column called % points to a pivot table called my_table that displays the percentage of total values in the points column.

The following example shows how to use this syntax in practice.

Example: Create Pandas Pivot Table With Percentages

Suppose we have the following pandas DataFrame that shows the number of points scored by various basketball players:

import pandas as pd

#create DataFrame
df = pd.DataFrame({'team': ['A', 'A', 'A', 'A', 'B', 'B', 'B', 'B'],
                   'position': ['Guard', 'Guard', 'Forward', 'Forward',
                                'Guard', 'Guard', 'Forward', 'Forward'],
                   'points': [22, 30, 14, 15, 19, 30, 23, 20]})

#view DataFrame
print(df)

  team position  points
0    A    Guard      22
1    A    Guard      30
2    A  Forward      14
3    A  Forward      15
4    B    Guard      19
5    B    Guard      30
6    B  Forward      23
7    B  Forward      20

We can use the pivot_table() function to create a pivot table that shows the sum of points by team and position:

#create pivot table to calculate sum of points by team and position
my_table = pd.pivot_table(df, index=['team', 'position'], aggfunc='sum')

#view pivot table
print(my_table)

               points
team position        
A    Forward       29
     Guard         52
B    Forward       43
     Guard         49

From the output we can see:

• Forwards on team A scored a total of 29 points.
• Guards on team A scored a total of 52 points.
• Forwards on team B scored a total of 43 points.
• Guards on team B scored a total of 49 points.

We can then use the following syntax to add a new column called % points that displays the percentage of the total points for each row:

#add column that displays points as a percentage of total points
my_table['% points'] = (my_table['points']/my_table['points'].sum())*100

#view updated pivot table
print(my_table)

               points   % points
team position                   
A    Forward       29  16.763006
     Guard         52  30.057803
B    Forward       43  24.855491
     Guard         49  28.323699

The new % points column now displays the points values as a percentage of total points.

Also note that you can use the round() function to round the percent values to a certain number of decimal places.

#add column that displays points as a percentage of total points (rounded)
my_table['% points'] = round((my_table['points']/my_table['points'].sum())*100, 2)

#view updated pivot table
print(my_table)

               points  % points
team position                  
A    Forward       29     16.76
     Guard         52     30.06
B    Forward       43     24.86
     Guard         49     28.32

The percentage values are now rounded to two decimal places.