Legend placement options in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the legend position in this plot?

Consider this matplotlib code snippet that plots two lines and adds a legend with loc='upper left'. What will be the position of the legend?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6], label='Line 1')
plt.plot([1, 2, 3], [6, 5, 4], label='Line 2')
plt.legend(loc='upper left')
plt.show()

A The legend appears at the bottom center inside the plot.

B The legend appears outside the plot area on the right side.

C The legend appears inside the plot area at the top-left corner.

D The legend appears outside the plot area at the top.

💡 Hint

Check the meaning of loc='upper left' in matplotlib legend placement.

The loc='upper left' option places the legend inside the plot area at the top-left corner.

❓ Predict Output

intermediate

What happens with loc='best' in legend?

Given this code, what does loc='best' do for the legend placement?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [1, 4, 9], label='Squares')
plt.plot([1, 2, 3], [1, 2, 3], label='Linear')
plt.legend(loc='best')
plt.show()

A Always places the legend at the center of the plot.

B Places the legend outside the plot area at the bottom.

C Raises an error because 'best' is not a valid location.

D Automatically places the legend in the location with least overlap with data.

💡 Hint

Think about what 'best' means for legend placement.

The loc='best' option lets matplotlib choose the location with the least overlap with plotted data.

🔧 Debug

advanced

Why does this legend placement code raise an error?

Examine the code below. Why does it raise an error when trying to place the legend?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [3, 2, 1], label='Descending')
plt.legend(loc='topright')
plt.show()

A Because 'topright' is not a valid legend location string in matplotlib.

B Because the plot has no labels to create a legend.

C Because the legend must be placed outside the plot area only.

D Because the plot command is missing a color argument.

💡 Hint

Check the valid location strings for legend placement in matplotlib.

Matplotlib does not recognize 'topright' as a valid location. Valid options include 'upper right', 'upper left', etc.

❓ data_output

advanced

How many legend entries appear with multiple plots and labels?

Given this code with multiple plots and labels, how many entries will the legend show?

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [1, 4, 9], label='Squares')
plt.plot([1, 2, 3], [1, 2, 3], label='Linear')
plt.plot([1, 2, 3], [9, 4, 1])  # No label
plt.legend(loc='lower right')
plt.show()

A 2 entries: Squares and Linear only.

B 1 entry: Only Squares.

C 3 entries: Squares, Linear, and the unlabeled plot.

D No entries because one plot has no label.

💡 Hint

Only plots with labels appear in the legend.

Only the plots with labels 'Squares' and 'Linear' appear in the legend. The unlabeled plot is ignored.

🚀 Application

expert

Which legend placement code places the legend outside the plot on the right?

You want to place the legend outside the plot area on the right side. Which code snippet achieves this?

A plt.legend(loc='upper right')

B plt.legend(loc='center left', bbox_to_anchor=(1, 0.5))

C plt.legend(loc='best')

D plt.legend(loc='lower left', bbox_to_anchor=(0, 0))

💡 Hint

Use bbox_to_anchor with loc to place legend outside plot.

Using loc='center left' with bbox_to_anchor=(1, 0.5) places the legend outside the plot on the right center.