Donut chart variation in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a donut chart?

A donut chart is a pie chart with a hole in the center. It shows parts of a whole, like a pie chart, but the center hole makes it easier to read and can hold labels or other info.

beginner

How do you create a donut chart using matplotlib?

You create a pie chart with matplotlib and add a white circle in the center to make a hole, turning it into a donut chart.

beginner

Why add a hole in the center of a pie chart to make a donut chart?

The hole reduces clutter and can hold text or labels, making the chart easier to understand and visually cleaner.

intermediate

What matplotlib function is used to draw the white circle in the center of a donut chart?

The function is plt.Circle(), which creates a circle patch that you add to the plot to create the hole.

intermediate

How can you add labels inside the hole of a donut chart in matplotlib?

You can use plt.text() to place text at the center coordinates of the chart, inside the hole.

What does a donut chart visually represent?

A A scatter plot with circles

B A bar chart with rounded edges

C A line chart with gaps

D Parts of a whole with a hole in the center

A donut chart is a pie chart with a hole in the center, showing parts of a whole.

Which matplotlib function helps create the hole in a donut chart?

A plt.Circle()

B plt.bar()

C plt.scatter()

D plt.plot()

plt.Circle() creates a circle patch that can be added to the plot to form the hole.

How do you add text inside the hole of a donut chart?

A Using plt.text() at the center coordinates

B Using plt.title()

C Using plt.xlabel()

D Using plt.legend()

plt.text() places text at specified coordinates, perfect for the center hole.

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

A Donut chart uses lines

B Pie chart has bars

C Donut chart has a hole in the center

D Pie chart has a legend

The donut chart is a pie chart with a hole in the center.

Why might you choose a donut chart over a pie chart?

A To show trends over time

B To add labels or info in the center hole

C To display data points

D To compare two variables

The hole in the donut chart can hold labels or extra info, improving clarity.

Explain how to create a donut chart using matplotlib step-by-step.

Think about how to turn a pie chart into a donut by adding a shape.

Describe the benefits of using a donut chart instead of a pie chart.

Consider what the hole adds to the chart.

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)