Labels, titles, and legends in Data Analysis Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the title of the plot?

Given the following Python code using matplotlib, what will be the title shown on the plot?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.title('Sales Over Time')
plt.xlabel('Month')
plt.ylabel('Revenue')
plt.show()

A Sales Over Time

B Sales Data

C Month

D Revenue

💡 Hint

Look for the plt.title() function argument.

The plt.title() function sets the title of the plot. Here, it is set to 'Sales Over Time'.

❓ data_output

intermediate

How many legend entries will appear?

Consider this code snippet that plots two lines with labels for the legend. How many entries will the legend show?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [1, 4, 9], label='Squares')
plt.plot([1, 2, 3], [1, 8, 27], label='Cubes')
plt.legend()
plt.show()

A 2

B 3

C 0

D 1

💡 Hint

Count how many lines have a label argument.

Two lines are plotted, each with a label. The legend shows one entry per labeled line, so it shows 2 entries.

🔧 Debug

advanced

Why does the legend not show?

This code plots two lines with labels but the legend does not appear. What is the reason?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [2, 4, 6], label='Double')
plt.plot([1, 2, 3], [3, 6, 9], label='Triple')
plt.show()

A The plt.show() function must be called before plotting lines.

B The labels are incorrect and cause an error preventing the legend.

C The plt.legend() function is missing, so no legend is displayed.

D The plot lines do not have colors, so the legend is hidden.

💡 Hint

Check if the legend function is called explicitly.

Matplotlib requires plt.legend() to be called to display the legend. Without it, labels exist but no legend is shown.

❓ visualization

advanced

Which option correctly adds a legend with a title?

You want to add a legend to your plot with the title 'Function Types'. Which code snippet does this correctly?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [1, 4, 9], label='Squares')
plt.plot([1, 2, 3], [1, 8, 27], label='Cubes')
# Add legend with title here
plt.show()

A plt.legend(legend_title='Function Types')

B plt.legend(label='Function Types')

C plt.legend(title_label='Function Types')

D plt.legend(title='Function Types')

💡 Hint

Check the official parameter name for legend title.

The correct parameter to add a title to the legend is 'title'. Other options are invalid and cause errors.

🧠 Conceptual

expert

What happens if you call plt.title() multiple times?

If you call plt.title('First Title') and then plt.title('Second Title') before plt.show(), what will be the plot's title?

Data Analysis Python

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [3, 2, 1])
plt.title('First Title')
plt.title('Second Title')
plt.show()

A The plot will show both titles concatenated.

B The plot will show 'Second Title' as the title.

C The plot will show 'First Title' as the title.

D The plot will have no title because of conflict.

💡 Hint

Think about how the title function updates the title property.

Each call to plt.title() replaces the previous title. The last call sets the final title.