How to calculate the Percentage of a column in Pandas ?

A Percentage is calculated by the mathematical formula of dividing the value by the sum of all the values and then multiplying the sum by 100. This is also applicable in Pandas Dataframes.

Here, the pre-defined sum() method of pandas series is used to compute the sum of all the values of a column.

Syntax: Series.sum()

Return: Returns the sum of the values.

Formula: 

df[percent] = (df['column_name'] / df['column_name'].sum()) * 100

Example 1: calculate the Percentage of a column in Pandas

Python3

# Import required libraries
import pandas as pd
import numpy as np

# Dictionary
df1 = {
     'Name': ['abc', 'bcd', 'cde',
             'def', 'efg', 'fgh',
             'ghi'],
     'Math_score': [52, 87, 49,
                   74, 28, 59,
                   48]}

# Create a DataFrame
df1 = pd.DataFrame(df1,
                   columns = ['Name',
                             'Math_score'])

# Calculating Percentage
df1['percent'] = (df1['Math_score'] /
                  df1['Math_score'].sum()) * 100

# Show the dataframe
df1

Output:

Example 2:

Python3

# Import pandas library
import pandas as pd

# Dictionary
df1 = {
     'Name': ['abc', 'bcd', 'cde',
             'def', 'efg', 'fgh',
             'ghi'],
      'Math_score': [52, 87, 49,
                    74, 28, 59,
                    48],
       'Eng_score': [34, 67, 25,
                    89, 92, 45,
                    86]
}

# Create a DataFrame
df1 = pd.DataFrame(df1,
                   columns = ['Name',
                   'Math_score','Eng_score'])

# Calculate Percentage
df1['Eng_percent'] = (df1['Eng_score'] /
                      df1['Eng_score'].sum()) * 100
# Show the dataframe
df1

Output: