Percentage labels in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of pie chart with percentage labels

What will be the output of this code snippet that creates a pie chart with percentage labels?

Matplotlib

import matplotlib.pyplot as plt
sizes = [15, 30, 45, 10]
labels = ['A', 'B', 'C', 'D']
plt.pie(sizes, labels=labels, autopct='%1.1f%%')
plt.show()

A A pie chart with four slices labeled A, B, C, D and percentages 15%, 30%, 45%, 10% without decimal places

B A pie chart with four slices labeled A, B, C, D but no percentage labels shown

C A pie chart with four slices labeled A, B, C, D and percentages 15.0%, 30.0%, 45.0%, 10.0% displayed on each slice

D A pie chart with four slices but labels are numbers 0, 1, 2, 3 instead of A, B, C, D

💡 Hint

Look at the autopct parameter format string '%1.1f%%' to understand the percentage format.

The autopct='%1.1f%%' formats the percentage with one decimal place and adds a percent sign. Labels are shown as given in the labels list.

🧠 Conceptual

intermediate

Understanding autopct parameter in pie charts

What does the autopct parameter do in matplotlib's pie chart function?

A It formats and displays the percentage value on each pie slice

B It sets the color of each pie slice

C It controls the size of the pie chart

D It adds a legend to the pie chart

💡 Hint

Think about what 'pct' in autopct might stand for.

The autopct parameter is used to display the percentage value on each slice of the pie chart, formatted as specified.

🔧 Debug

advanced

Identify the error in percentage label formatting

What error will this code produce when trying to add percentage labels to a pie chart? import matplotlib.pyplot as plt sizes = [10, 20, 30] labels = ['X', 'Y', 'Z'] plt.pie(sizes, labels=labels, autopct='%1.f%%') plt.show()

A ValueError because '%1.f%%' is an invalid format specifier

B No error; the pie chart shows percentages without decimal places

C TypeError because autopct expects a function, not a string

D SyntaxError due to incorrect format string in autopct

💡 Hint

Check if '%1.f%%' is a valid Python format specifier for floats.

The format specifier '%1.f%%' is invalid because after the decimal point '.', a precision digit is required (e.g., '%1.0f%%'). This causes a ValueError.

❓ data_output

advanced

Resulting labels with custom autopct function

Given this code, what is the output of the labels shown on the pie chart slices? import matplotlib.pyplot as plt sizes = [25, 25, 50] labels = ['Red', 'Blue', 'Green'] def func(pct): return f'{pct:.0f}%% of total' plt.pie(sizes, labels=labels, autopct=func) plt.show()

A Slices labeled 'Red', 'Blue', 'Green' with percentages '25.0%', '25.0%', '50.0%'

B Slices labeled 'Red', 'Blue', 'Green' with percentages '25%% of total', '25%% of total', '50%% of total'

C Slices labeled 'Red', 'Blue', 'Green' with no percentage labels

D Slices labeled 'Red', 'Blue', 'Green' with percentages '25% of total', '25% of total', '50% of total'

💡 Hint

Look at the custom function formatting the percentage string.

The custom function formats the percentage with no decimals and adds ' of total' text after the percent sign.

🚀 Application

expert

Creating a pie chart with percentage labels and exploded slice

Which code snippet correctly creates a pie chart with percentage labels showing one decimal place, labels for each slice, and the largest slice exploded outward?

A

import matplotlib.pyplot as plt
sizes = [10, 20, 30, 40]
labels = ['A', 'B', 'C', 'D']
explode = [0.1, 0, 0, 0]
plt.pie(sizes, labels=labels, autopct='%1.1f%%', explode=explode)
plt.show()

B

import matplotlib.pyplot as plt
sizes = [10, 20, 30, 40]
labels = ['A', 'B', 'C', 'D']
explode = [0, 0, 0, 0.1]
plt.pie(sizes, labels=labels, autopct='%1.1f%%', explode=explode)
plt.show()

C

import matplotlib.pyplot as plt
sizes = [10, 20, 30, 40]
labels = ['A', 'B', 'C', 'D']
explode = [0, 0, 0, 0.1]
plt.pie(sizes, labels=labels, autopct='%1.0f%%', explode=explode)
plt.show()

D

import matplotlib.pyplot as plt
sizes = [10, 20, 30, 40]
labels = ['A', 'B', 'C', 'D']
explode = [0, 0, 0, 0.1]
plt.pie(sizes, labels=labels, autopct='%1.1f', explode=explode)
plt.show()

💡 Hint

The largest slice is 40, so explode should highlight that slice. Check the autopct format for one decimal place and percent sign.

Option B explodes the largest slice (index 3) with 0.1 offset, uses autopct='%1.1f%%' to show one decimal place and percent sign correctly.