Why pie charts show proportions in Matplotlib - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to create a pie chart showing proportions of fruits.

Matplotlib

import matplotlib.pyplot as plt

sizes = [30, 45, 25]
labels = ['Apples', 'Bananas', 'Cherries']
plt.pie(sizes, labels=[1])
plt.show()

Drag options to blanks, or click blank then click option'

Alabels

Bcolors

Csizes

Dexplode

Attempts:

3 left

💡 Hint

Common Mistakes

Using the sizes list instead of labels for the labels parameter.

Confusing colors or explode parameters with labels.

The labels parameter adds names to each slice, showing what each proportion represents.

2fill in blank

medium

Complete the code to add percentages on each pie slice.

Matplotlib

plt.pie(sizes, labels=labels, autopct=[1])
plt.show()

Drag options to blanks, or click blank then click option'

A'%s%%'

B'%d%%'

C'%.1f%%'

D'%%.1f'

Attempts:

3 left

💡 Hint

Common Mistakes

Using '%d%%' which shows no decimal places.

Using incorrect format strings that cause errors.

The autopct parameter formats the percentage text on slices. '%.1f%%' shows one decimal place.

3fill in blank

hard

Fix the error in the code to correctly display the pie chart with a shadow.

Matplotlib

plt.pie(sizes, labels=labels, autopct='%.1f%%', [1]=True)
plt.show()

Drag options to blanks, or click blank then click option'

Ashadow

Bshadows

Cshadowed

Dshow_shadow

Attempts:

3 left

💡 Hint

Common Mistakes

Using incorrect parameter names like 'shadows' or 'shadowed'.

Trying to add shadow with unsupported parameters.

The correct parameter to add a shadow is shadow=True.

4fill in blank

hard

Fill both blanks to create a pie chart with exploded slices and a start angle.

Matplotlib

explode = ([1], [2], 0)
plt.pie(sizes, labels=labels, explode=explode, startangle=90)
plt.show()

Drag options to blanks, or click blank then click option'

A0.1

B0.2

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using integers like 1 which explode slices too much.

Using negative numbers which cause errors.

The first slice is exploded by 0.1, the second slice is not exploded (0).

5fill in blank

hard

Fill all three blanks to create a pie chart with colors, shadow, and percentage format.

Matplotlib

colors = ['gold', 'yellowgreen', [1]]
plt.pie(sizes, labels=labels, colors=colors, autopct=[2], [3]=True)
plt.show()

Drag options to blanks, or click blank then click option'

A'lightcoral'

B'%.0f%%'

Cshadow

D'blue'

Attempts:

3 left

💡 Hint

Common Mistakes

Using invalid color names or missing quotes.

Wrong format strings for autopct causing errors.

Incorrect parameter name for shadow.

The third color is 'lightcoral', percentages show no decimals with '%.0f%%', and shadow is enabled with shadow=True.

Practice

1. Why do pie charts show slices of different sizes?

easy

A. Because each slice represents a proportion of the total

B. Because slices are randomly sized

C. Because all slices must be equal

D. Because slices represent unrelated data points

Solution

1. Step 1: Understand what pie chart slices represent

   Each slice shows a part of the whole data set.

2. Step 2: Connect slice size to proportion

   The size of each slice matches how big that part is compared to the total.

3. Final Answer:

   Because each slice represents a proportion of the total -> Option A

4. Quick Check:

   Slice size = proportion [OK]

Hint: Remember: pie slices show parts of a whole [OK]

Common Mistakes:

• Thinking slices are random sizes
• Assuming all slices are equal
• Believing slices show unrelated data

2. Which matplotlib function is used to create a pie chart?

easy

A. plt.bar()

B. plt.pie()

C. plt.scatter()

D. plt.plot()

Solution

1. Step 1: Recall matplotlib plotting functions

   Matplotlib has specific functions for different chart types.

2. Step 2: Identify the pie chart function

   The function plt.pie() is designed to create pie charts.

3. Final Answer:

   plt.pie() -> Option B

4. Quick Check:

   Pie chart = plt.pie() [OK]

Hint: Pie chart uses plt.pie() function [OK]

Common Mistakes:

• Using plt.bar() for pie charts
• Confusing plt.scatter() with pie charts
• Trying plt.plot() for pie charts

3. What will the following code output?

import matplotlib.pyplot as plt
sizes = [30, 70]
plt.pie(sizes, labels=['A', 'B'])
plt.show()

medium

A. A line plot connecting points 30 and 70

B. A bar chart with two bars of heights 30 and 70

C. An error because labels are missing

D. A pie chart with two slices sized 30% and 70%

Solution

1. Step 1: Analyze the plt.pie() call

   The sizes list has two values: 30 and 70, which sum to 100.

2. Step 2: Understand labels and output

   Labels 'A' and 'B' correspond to slices sized 30% and 70% of the pie.

3. Final Answer:

   A pie chart with two slices sized 30% and 70% -> Option D

4. Quick Check:

   Pie slices match sizes list [OK]

Hint: Pie slices match sizes list values [OK]

Common Mistakes:

• Confusing pie chart with bar chart
• Expecting error due to labels
• Thinking it creates a line plot

4. Identify the error in this pie chart code:

import matplotlib.pyplot as plt
sizes = [20, 30, 50]
plt.pie(sizes, labels=['X', 'Y'])
plt.show()

medium

A. The sizes list has invalid values

B. plt.pie() cannot plot more than two slices

C. The labels list length does not match sizes list length

D. plt.show() is missing

Solution

1. Step 1: Check sizes and labels lengths

   Sizes has 3 values, labels has only 2 labels.

2. Step 2: Understand matplotlib requirements

   Labels must match the number of slices to label each slice properly.

3. Final Answer:

   The labels list length does not match sizes list length -> Option C

4. Quick Check:

   Labels count = sizes count [OK]

Hint: Labels count must equal sizes count [OK]

Common Mistakes:

• Thinking sizes values are invalid
• Believing plt.pie() limits slices
• Forgetting plt.show() is needed

5. You want to show proportions of sales for 4 products using a pie chart. The sales are [100, 200, 300, 400]. How do you ensure the pie chart correctly shows proportions?

hard

A. Pass the sales list directly to plt.pie() and add labels for each product

B. Normalize sales to percentages before passing to plt.pie()

C. Use plt.bar() instead because pie charts need percentages

D. Divide each sales value by 1000 before plotting

Solution

1. Step 1: Understand how plt.pie() works with data

   Matplotlib automatically calculates proportions from raw values.

2. Step 2: Confirm labels and data match

   Passing raw sales with matching labels shows correct slice sizes.

3. Final Answer:

   Pass the sales list directly to plt.pie() and add labels for each product -> Option A

4. Quick Check:

   Raw values work; no manual normalization needed [OK]

Hint: Pass raw values; matplotlib calculates proportions [OK]

Common Mistakes:

• Thinking manual percentage calculation is needed
• Using bar chart instead of pie chart
• Scaling values unnecessarily