Pie chart color customization in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What colors will the pie chart slices have?

Consider this code that creates a pie chart with custom colors. What colors will the slices be?

Matplotlib

import matplotlib.pyplot as plt
sizes = [30, 20, 50]
colors = ['red', 'green', 'blue']
plt.pie(sizes, colors=colors)
plt.show()

A Slices colored all gray

B Slices colored default matplotlib colors ignoring the list

C Slices colored red, green, and blue respectively

D Slices colored yellow, cyan, and magenta

💡 Hint

The colors list is passed to the pie function to set slice colors.

The colors parameter in plt.pie sets the slice colors in order. Here, red, green, and blue are used.

❓ data_output

intermediate

How many slices will be colored orange?

Given this pie chart code, how many slices will be orange?

Matplotlib

import matplotlib.pyplot as plt
sizes = [10, 20, 30, 40]
colors = ['orange', 'orange', 'blue', 'green']
plt.pie(sizes, colors=colors)
plt.show()

A 2 slices

B 1 slice

C 3 slices

D 0 slices

💡 Hint

Count how many times 'orange' appears in the colors list.

The colors list has 'orange' twice, so two slices will be orange.

🔧 Debug

advanced

Why does this pie chart ignore the colors list?

This code tries to color slices but all slices appear gray. What is the error?

Matplotlib

import matplotlib.pyplot as plt
sizes = [25, 25, 25, 25]
colors = ['red', 'green', 'blue', 'yellow']
plt.pie(sizes, color=colors)
plt.show()

A The pie function does not accept a colors parameter

B The sizes list must be strings, not integers

C The colors list must have hex codes, not names

D The parameter should be 'colors', not 'color'

💡 Hint

Check the exact parameter name for slice colors in plt.pie.

The correct parameter name is 'colors'. Using 'color' is ignored, so default colors appear.

❓ visualization

advanced

Which option shows a pie chart with a custom color palette?

You want a pie chart with slices colored purple, orange, and teal. Which code produces this?

A plt.pie([40, 30, 30], colors=['purple', 'orange', 'teal'])

B plt.pie([40, 30, 30], color=['purple', 'orange', 'teal'])

C plt.pie([40, 30, 30], colors=['red', 'green', 'blue'])

D plt.pie([40, 30, 30], colors=['purple', 'orange'])

💡 Hint

Use the correct parameter name and provide one color per slice.

Option A uses the correct 'colors' parameter with three colors matching three slices.

🚀 Application

expert

How to create a pie chart with alternating slice colors?

You want a pie chart with 6 slices where colors alternate between 'red' and 'blue'. Which code creates this pattern?

A

colors = ['red', 'blue'] * 3
plt.pie([10]*6, color=colors)
plt.show()

B

colors = ['red' if i % 2 == 0 else 'blue' for i in range(6)]
plt.pie([10]*6, colors=colors)
plt.show()

C

colors = ['red', 'blue', 'red', 'blue', 'red', 'blue']
plt.pie([10]*6, colors=colors)
plt.show()

D

colors = ['red', 'blue']
plt.pie([10]*6, colors=colors)
plt.show()

💡 Hint

Use a list comprehension to generate the alternating colors list.

Option B dynamically creates a list of 6 colors alternating red and blue, matching slice count.

Practice

1. What does the colors parameter do in a matplotlib pie chart?

easy

A. It changes the size of the pie chart.

B. It changes the chart title.

C. It adds labels to the pie slices.

D. It sets the colors of each slice in the pie chart.

Solution

1. Step 1: Understand the role of colors in pie charts

   The colors parameter is used to specify the colors for each slice of the pie chart.

2. Step 2: Compare with other options

   Options A, C, and D relate to size, labels, and title, which are controlled by other parameters.

3. Final Answer:

   It sets the colors of each slice in the pie chart. -> Option D

4. Quick Check:

   colors parameter = slice colors [OK]

Hint: Remember: colors parameter controls slice colors [OK]

Common Mistakes:

• Confusing colors with labels
• Thinking colors change chart size
• Mixing colors with title settings

2. Which of the following is the correct way to set colors in a matplotlib pie chart?

easy

A. plt.pie(data, colors=['red', 'blue', 'green'])

B. plt.pie(data, color=['red', 'blue', 'green'])

C. plt.pie(data, col=['red', 'blue', 'green'])

D. plt.pie(data, set_colors=['red', 'blue', 'green'])

Solution

1. Step 1: Recall the correct parameter name

   The correct parameter to set slice colors is colors, not color, col, or set_colors.

2. Step 2: Check syntax correctness

   plt.pie(data, colors=['red', 'blue', 'green']) uses colors with a list of color names, which is the correct syntax.

3. Final Answer:

   plt.pie(data, colors=['red', 'blue', 'green']) -> Option A

4. Quick Check:

   Use colors= list for slice colors [OK]

Hint: Use exact parameter name 'colors' for slice colors [OK]

Common Mistakes:

• Using 'color' instead of 'colors'
• Using undefined parameters like 'col' or 'set_colors'
• Passing colors as a string instead of a list

3. What will be the color of the second slice in this code?

import matplotlib.pyplot as plt
sizes = [30, 40, 30]
colors = ['#FF0000', '#00FF00', '#0000FF']
plt.pie(sizes, colors=colors)
plt.show()

medium

A. Blue

B. Red

C. Green

D. Black

Solution

1. Step 1: Identify the colors list order

   The colors list is ['#FF0000', '#00FF00', '#0000FF'], which correspond to red, green, and blue in order.

2. Step 2: Match the second slice color

   The second slice uses the second color '#00FF00', which is green.

3. Final Answer:

   Green -> Option C

4. Quick Check:

   Second color in list = green [OK]

Hint: Colors list order matches slice order [OK]

Common Mistakes:

• Mixing hex codes with color names
• Assuming default colors override given list
• Confusing slice index starting at 0 or 1

4. Find the error in this pie chart color code:

import matplotlib.pyplot as plt
sizes = [25, 25, 50]
colors = 'red, blue, green'
plt.pie(sizes, colors=colors)
plt.show()

medium

A. colors should be a list, not a string

B. sizes list has wrong values

C. plt.pie does not accept colors parameter

D. Missing plt.show() call

Solution

1. Step 1: Check the type of colors parameter

   The colors parameter must be a list of color names or hex codes, but here it is a single string.

2. Step 2: Understand the impact of wrong type

   Passing a string will cause matplotlib to treat it as one color or raise an error.

3. Final Answer:

   colors should be a list, not a string -> Option A

4. Quick Check:

   colors must be list, not string [OK]

Hint: Always pass colors as a list, not a single string [OK]

Common Mistakes:

• Passing colors as comma-separated string
• Ignoring type requirements for colors
• Assuming plt.show() is optional

5. You want to create a pie chart with 4 slices and use custom colors: red, green, blue, and yellow. Which code correctly applies these colors and also adds labels for each slice?

hard

A. plt.pie([10, 20, 30, 40], colors=['red', 'green', 'blue', 'yellow'], label=['A', 'B', 'C', 'D'])

B. plt.pie([10, 20, 30, 40], colors=['red', 'green', 'blue', 'yellow'], labels=['A', 'B', 'C', 'D'])

C. plt.pie([10, 20, 30, 40], colors=['red', 'green', 'blue'], labels=['A', 'B', 'C', 'D'])

D. plt.pie([10, 20, 30, 40], color=['red', 'green', 'blue', 'yellow'], labels=['A', 'B', 'C', 'D'])

Solution

1. Step 1: Verify the colors parameter and list length

   The colors parameter must be named exactly 'colors' and have 4 colors for 4 slices.

2. Step 2: Check the labels parameter name and length

   The labels parameter must be named 'labels' and have 4 labels matching the slices.

3. Step 3: Identify errors in other options

   plt.pie([10, 20, 30, 40], color=['red', 'green', 'blue', 'yellow'], labels=['A', 'B', 'C', 'D']) uses 'color' instead of 'colors'. plt.pie([10, 20, 30, 40], colors=['red', 'green', 'blue'], labels=['A', 'B', 'C', 'D']) has only 3 colors for 4 slices. plt.pie([10, 20, 30, 40], colors=['red', 'green', 'blue', 'yellow'], label=['A', 'B', 'C', 'D']) uses 'label' instead of 'labels'.

4. Final Answer:

   plt.pie([10, 20, 30, 40], colors=['red', 'green', 'blue', 'yellow'], labels=['A', 'B', 'C', 'D']) -> Option B

5. Quick Check:

   Use colors= and labels= with matching list lengths [OK]

Hint: Match colors and labels list lengths with data slices [OK]

Common Mistakes:

• Using wrong parameter names like 'color' or 'label'
• Mismatched list lengths for colors or labels
• Forgetting to pass labels parameter