Donut chart variation in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple donut chart code

What will be the output of this code snippet that creates a donut chart using matplotlib?

Matplotlib

import matplotlib.pyplot as plt

sizes = [30, 20, 50]
labels = ['A', 'B', 'C']

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

A A pie chart with three slices labeled A, B, C but no hole in the center

B An error because wedgeprops is not a valid argument

C A bar chart with three bars labeled A, B, C

D A pie chart with three slices labeled A, B, C and a hole in the center (donut shape)

💡 Hint

Look at the wedgeprops argument and what width controls in a pie chart.

The wedgeprops argument with width less than 1 creates a donut chart by making a hole in the center of the pie chart.

❓ data_output

intermediate

Number of wedges in a donut chart

Given this code, how many wedges (slices) will the donut chart display?

Matplotlib

import matplotlib.pyplot as plt

sizes = [10, 15, 25, 50]
labels = ['W', 'X', 'Y', 'Z']

plt.pie(sizes, labels=labels, wedgeprops=dict(width=0.3))
plt.show()

A 4

B 3

C 1

D 0

💡 Hint

Count the number of elements in the sizes list.

Each element in sizes corresponds to one wedge in the pie or donut chart.

❓ visualization

advanced

Effect of changing width in donut chart

What visual difference will you see if you change the width in wedgeprops from 0.5 to 0.9 in this donut chart code?

Matplotlib

import matplotlib.pyplot as plt

sizes = [40, 30, 30]
labels = ['Red', 'Green', 'Blue']

plt.pie(sizes, labels=labels, wedgeprops=dict(width=0.5))
plt.show()

A The hole in the center becomes larger, making the donut thinner

B The chart changes to a normal pie chart with no hole

C The hole in the center becomes smaller, making the donut thicker

D The chart disappears because width 0.9 is invalid

💡 Hint

Width controls the thickness of the donut ring; higher width means thicker ring.

Increasing width closer to 1 increases the thickness of the donut ring, making the hole smaller.

🔧 Debug

advanced

Identify the error in donut chart code

What error will this code raise when trying to create a donut chart?

Matplotlib

import matplotlib.pyplot as plt

sizes = [25, 25, 25, 25]
labels = ['Q1', 'Q2', 'Q3', 'Q4']

plt.pie(sizes, labels=labels, wedgeprops={'width': 1.2})
plt.show()

A ValueError because width cannot be greater than 1

B TypeError because wedgeprops must be a dict with string keys

C No error, chart displays normally

D SyntaxError due to wrong dictionary syntax

💡 Hint

Width controls the thickness of the donut ring and must be between 0 and 1.

Width greater than 1 is invalid and causes a ValueError in matplotlib pie charts.

🚀 Application

expert

Customize donut chart with exploded slice

Which code snippet correctly creates a donut chart with the second slice exploded outward?

A plt.pie([20, 30, 50], labels=['X', 'Y', 'Z'], wedgeprops=dict(width=0.4), explode=[0.1, 0, 0])

B plt.pie([20, 30, 50], labels=['X', 'Y', 'Z'], wedgeprops=dict(width=0.4), explode=[0, 0.1, 0])

C plt.pie([20, 30, 50], labels=['X', 'Y', 'Z'], wedgeprops=dict(width=0.4), explode=[0, 0, 0.1])

D plt.pie([20, 30, 50], labels=['X', 'Y', 'Z'], wedgeprops=dict(width=0.4), explode=[0.1, 0.1, 0])

💡 Hint

The explode list controls how far each slice is offset; the second slice is index 1.

To explode the second slice, only the second value in explode should be non-zero.

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)