Legend outside the plot in Matplotlib - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the position of the legend in this plot?

Consider the following Python code using matplotlib. What will be the position of the legend relative to the plot?

Matplotlib

import matplotlib.pyplot as plt

plt.plot([1, 2, 3], label='Line 1')
plt.plot([3, 2, 1], label='Line 2')
plt.legend(loc='center left', bbox_to_anchor=(1, 0.5))
plt.show()

A The legend is inside the plot area at the bottom left corner.

B The legend is inside the plot area at the top right corner.

C The legend is outside the plot area on the right, vertically centered.

D The legend is below the plot, centered horizontally.

💡 Hint

Look at the bbox_to_anchor coordinates and the loc parameter.

The loc='center left' places the legend's center left point at the coordinates given by bbox_to_anchor=(1, 0.5). This means the legend is placed outside the plot on the right side, vertically centered.

❓ data_output

intermediate

How many legend entries will appear?

Given the following code, how many entries will the legend display?

Matplotlib

import matplotlib.pyplot as plt

plt.plot([1, 2, 3], label='A')
plt.plot([3, 2, 1])
plt.plot([2, 2, 2], label='B')
plt.legend(loc='upper left', bbox_to_anchor=(1, 1))
plt.show()

A 1

B 2

C 3

D 0

💡 Hint

Only lines with a label are shown in the legend.

Only the first and third lines have labels ('A' and 'B'), so the legend shows 2 entries.

❓ visualization

advanced

Identify the correct code to place the legend outside below the plot

Which code snippet correctly places the legend centered below the plot area?

A plt.legend(loc='center right', bbox_to_anchor=(0.5, -0.1), ncol=2)

B plt.legend(loc='lower center', bbox_to_anchor=(0.5, -0.1), ncol=2)

C plt.legend(loc='center', bbox_to_anchor=(0.5, -0.1), ncol=2)

D plt.legend(loc='upper center', bbox_to_anchor=(0.5, -0.1), ncol=2)

💡 Hint

Think about the legend anchor point and its position below the plot.

Using loc='upper center' with bbox_to_anchor=(0.5, -0.1) places the legend below the plot, centered horizontally. The ncol=2 arranges legend entries in two columns.

🔧 Debug

advanced

Why does this legend not appear outside the plot?

Examine the code below. The user wants the legend outside the plot on the right, but it appears inside. Why?

Matplotlib

import matplotlib.pyplot as plt

plt.plot([1, 2, 3], label='X')
plt.legend(loc='right', bbox_to_anchor=(1, 0.5))
plt.show()

A loc='right' anchors the midpoint of the legend's right side to (1, 0.5), causing it to extend inside the plot; use 'center left' instead.

B The bbox_to_anchor coordinates are outside the plot, so legend is hidden.

C The plot has no labels, so legend is empty and not shown.

D The legend is outside but the figure size is too small to see it.

💡 Hint

Consider what point of the legend loc='right' places at bbox_to_anchor.

loc='right' is valid, but it places the midpoint of the legend's right edge at bbox_to_anchor=(1, 0.5). This causes the legend to extend leftward into the plot area. To place the legend outside on the right, use loc='center left', which places the legend's left edge at the axes right edge.

🚀 Application

expert

How to ensure legend outside plot does not overlap with figure content?

You want to place the legend outside the plot on the right side without overlapping the plot content. Which approach is best?

A Use <code>plt.legend(loc='center left', bbox_to_anchor=(1, 0.5))</code> and adjust <code>plt.subplots_adjust(right=0.75)</code> to shrink plot area.

B Use <code>plt.legend(loc='center left', bbox_to_anchor=(1, 0.5))</code> only, no other adjustments needed.

C Increase figure size only with <code>plt.figure(figsize=(10,6))</code> without changing legend position.

D Place legend inside plot with <code>loc='best'</code> to avoid overlap.

💡 Hint

Think about how to make space for the legend outside the plot area.

Placing the legend outside requires shrinking the plot area using plt.subplots_adjust so the plot and legend do not overlap. Just placing the legend outside without adjusting the plot area causes overlap.