Why pie charts show proportions in Matplotlib

Introduction

Pie charts help us see how parts make up a whole. They show proportions by dividing a circle into slices.

You want to show how different categories share a total, like favorite fruits in a group.

You need to compare parts of a budget to the total spending.

You want to display survey results as percentages of all answers.

You want to quickly show which category is biggest or smallest in a dataset.

Syntax

Matplotlib

matplotlib.pyplot.pie(sizes, labels=None, autopct=None, startangle=0)

sizes is a list of numbers representing each slice size.

labels names each slice.

Examples

Simple pie chart with two slices showing 30 and 70 parts.

Matplotlib

sizes = [30, 70]
plt.pie(sizes)
plt.show()

Pie chart with labels for each slice.

Matplotlib

sizes = [10, 20, 30]
labels = ['A', 'B', 'C']
plt.pie(sizes, labels=labels)
plt.show()

Pie chart showing percentage values on each slice.

Matplotlib

sizes = [15, 35, 50]
labels = ['X', 'Y', 'Z']
plt.pie(sizes, labels=labels, autopct='%1.1f%%')
plt.show()

Sample Program

This program creates a pie chart showing how three fruits share a total. The percentages show each fruit's part of the whole.

Matplotlib

import matplotlib.pyplot as plt

sizes = [25, 35, 40]
labels = ['Apples', 'Bananas', 'Cherries']

plt.pie(sizes, labels=labels, autopct='%1.1f%%', startangle=90)
plt.title('Fruit Proportions')
plt.show()

Important Notes

Pie charts work best with a small number of categories.

Percentages help understand the size of each slice easily.

Start angle rotates the chart for better view.

Summary

Pie charts divide a circle to show parts of a whole.

They use slice sizes to represent proportions.

Labels and percentages make the chart easier to read.