Donut chart variation in Matplotlib

Introduction

A donut chart helps show parts of a whole, like a pie chart, but with a hole in the middle. This makes it easier to read and looks nice.

Showing how different categories contribute to a total, like sales by product type.

Comparing proportions in a survey, such as favorite ice cream flavors.

Visualizing budget spending across departments with a clear center space.

Displaying election results by party share with a clean look.

Syntax

Matplotlib

import matplotlib.pyplot as plt

sizes = [30, 20, 25, 25]
labels = ['A', 'B', 'C', 'D']

plt.pie(sizes, labels=labels, wedgeprops=dict(width=0.4))
plt.show()

The wedgeprops argument controls the thickness of the donut ring.

Setting width less than 1 creates the hole in the middle.

Examples

A simple donut chart with two parts and a thin ring.

Matplotlib

plt.pie([40, 60], labels=['Yes', 'No'], wedgeprops=dict(width=0.3))
plt.show()

Donut chart rotated to start at 90 degrees for better layout.

Matplotlib

plt.pie([10, 20, 30], labels=['X', 'Y', 'Z'], wedgeprops=dict(width=0.5), startangle=90)
plt.show()

Donut chart showing percentages inside each slice.

Matplotlib

plt.pie([25, 25, 25, 25], labels=['Q1', 'Q2', 'Q3', 'Q4'], wedgeprops=dict(width=0.4), autopct='%1.1f%%')
plt.show()

Sample Program

This program creates a donut chart showing fruit distribution with colors and percentages.

Matplotlib

import matplotlib.pyplot as plt

# Data for the chart
sizes = [15, 30, 45, 10]
labels = ['Apples', 'Bananas', 'Cherries', 'Dates']
colors = ['#ff9999','#66b3ff','#99ff99','#ffcc99']

# Create donut chart
plt.pie(sizes, labels=labels, colors=colors, autopct='%1.1f%%', startangle=140, wedgeprops=dict(width=0.5))

# Add a title
plt.title('Fruit Distribution')

# Show the plot
plt.show()

Important Notes

Donut charts are easier to read when the hole is not too small or too large.

Use autopct to add percentage labels inside slices.

Colors help distinguish categories clearly.

Summary

Donut charts are pie charts with a hole in the center.

Use wedgeprops=dict(width=...) to create the hole.

They help show parts of a whole in a clean, readable way.

Practice

1.

What is the main difference between a donut chart and a pie chart in matplotlib?

easy

A. A donut chart has a hole in the center, a pie chart does not.

B. A donut chart uses bars, a pie chart uses slices.

C. A donut chart shows data over time, a pie chart shows categories.

D. A donut chart is 3D, a pie chart is 2D.

Solution

1. Step 1: Understand pie chart basics

   A pie chart divides a circle into slices representing parts of a whole.

2. Step 2: Identify donut chart feature

   A donut chart is a pie chart with a hole in the center, making it look like a donut.

3. Final Answer:

   A donut chart has a hole in the center, a pie chart does not. -> Option A

4. Quick Check:

   Donut chart = pie chart + hole [OK]

Hint: Donut chart = pie chart with center hole [OK]

Common Mistakes:

• Thinking donut charts use bars
• Confusing donut charts with 3D charts
• Believing donut charts show time series

2.

Which matplotlib code snippet correctly creates a donut chart with a hole size controlled by wedgeprops?

import matplotlib.pyplot as plt
sizes = [30, 40, 30]
plt.pie(sizes, wedgeprops=???)
plt.show()

easy

A. wedgeprops={'height': 0.5}

B. wedgeprops={'radius': 0.5}

C. wedgeprops={'width': 0.5}

D. wedgeprops={'size': 0.5}

Solution

1. Step 1: Recall donut hole control

   The hole size in a donut chart is set by the 'width' key inside wedgeprops.

2. Step 2: Match correct syntax

   Using wedgeprops={'width': 0.5} creates a hole half the radius size.

3. Final Answer:

   wedgeprops={'width': 0.5} -> Option C

4. Quick Check:

   wedgeprops width controls hole size [OK]

Hint: Use wedgeprops={'width': value} for donut hole [OK]

Common Mistakes:

• Using 'radius' instead of 'width'
• Using 'height' or 'size' keys incorrectly
• Omitting wedgeprops entirely

3.

What will be the visual output of this code?

import matplotlib.pyplot as plt
sizes = [10, 20, 30]
plt.pie(sizes, wedgeprops={'width': 0.3})
plt.show()

medium

A. A donut chart with a thin ring shape

B. A pie chart with no hole in the center

C. A donut chart with a very large hole

D. A bar chart instead of a pie chart

Solution

1. Step 1: Analyze wedgeprops width value

   The width is set to 0.3, meaning the donut hole is 70% of the radius.

2. Step 2: Visualize the chart shape

   This creates a donut chart with a thin ring shape because the hole is large but not full radius.

3. Final Answer:

   A donut chart with a thin ring shape -> Option A

4. Quick Check:

   width=0.3 means thin donut ring [OK]

Hint: Smaller width = thinner donut ring [OK]

Common Mistakes:

• Thinking width=0.3 means no hole
• Confusing hole size with radius
• Expecting a bar chart output

4.

Identify the error in this donut chart code and select the fix:

import matplotlib.pyplot as plt
sizes = [25, 35, 40]
plt.pie(sizes, wedgeprops={'width': '0.5'})
plt.show()

medium

A. Add labels parameter

B. Remove wedgeprops entirely

C. Change 'width' to 'radius'

D. Change '0.5' to 0.5 (string to float)

Solution

1. Step 1: Check wedgeprops value type

   The width value is given as a string '0.5', but it must be a number (float).

2. Step 2: Correct the data type

   Changing '0.5' to 0.5 fixes the type error and creates the donut hole properly.

3. Final Answer:

   Change '0.5' to 0.5 (string to float) -> Option D

4. Quick Check:

   width must be float, not string [OK]

Hint: Use numbers, not strings, for wedgeprops values [OK]

Common Mistakes:

• Using string instead of float for width
• Changing width key incorrectly
• Ignoring type errors

5.

You want to create a donut chart showing sales distribution with a hole size that leaves 40% thickness for the slices. Which wedgeprops value should you use?

hard

A. wedgeprops={'width': 0.4}

B. wedgeprops={'width': 0.6}

C. wedgeprops={'width': 0.2}

D. wedgeprops={'width': 1.0}

Solution

1. Step 1: Understand width meaning

   The 'width' value is the thickness of the slices as a fraction of the radius.

2. Step 2: Calculate width for 40% thickness

   For 40% thickness for the slices, set width=0.6 (leaving a hole size of 40%).

3. Final Answer:

   wedgeprops={'width': 0.6} -> Option B

4. Quick Check:

   width=0.6 gives 40% slice thickness [OK]

Hint: Width = slice thickness fraction (1 - hole size) [OK]

Common Mistakes:

• Confusing width with hole size
• Using width less than hole thickness
• Setting width to 1 (no hole)