Legend outside the plot in Matplotlib - Step-by-Step Execution

Concept Flow - Legend outside the plot

Create plot with data

↓

Add legend inside plot

↓

Adjust legend position

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Place legend outside plot area

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Display final plot

This flow shows how to create a plot, add a legend, then move the legend outside the plot area for better visibility.

Execution Sample

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()

This code plots two lines and places the legend outside the plot on the right side.

Execution Table

Step	Action	Legend Location	Legend Coordinates	Plot Displayed
1	Plot line 1 with label 'Line 1'	None	None	No
2	Plot line 2 with label 'Line 2'	None	None	No
3	Add legend with default location	Best (inside plot)	(default)	No
4	Change legend location to 'center left' outside plot	center left	(1, 0.5)	No
5	Show plot with legend outside	center left	(1, 0.5)	Yes

💡 Plot displayed with legend outside on the right at coordinates (1, 0.5)

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4	Final
legend location	None	None	None	best (inside)	center left	center left
legend bbox_to_anchor	None	None	None	default	(1, 0.5)	(1, 0.5)
plot displayed	False	False	False	False	False	True

Key Moments - 3 Insights

Why does the legend appear inside the plot before setting bbox_to_anchor?

By default, plt.legend() places the legend inside the plot at the 'best' location. This is shown in execution_table step 3 where the legend location is 'best (inside)'.

What does bbox_to_anchor=(1, 0.5) do to the legend position?

bbox_to_anchor sets the anchor point for the legend box. (1, 0.5) places it at the right center outside the plot area, as seen in step 4 and 5.

Why is the plot not displayed until plt.show() is called?

Matplotlib builds the plot step-by-step but only renders it on screen when plt.show() is called, as indicated by 'plot displayed' changing to True at step 5.

Visual Quiz - 3 Questions

Look at the execution_table at step 4, where is the legend positioned?

A Outside the plot on the right center

B Inside the plot at the best location

C At the top left corner inside the plot

D At the bottom center inside the plot

💡 Hint

Check the 'Legend Location' and 'Legend Coordinates' columns at step 4 in execution_table

According to variable_tracker, when does 'plot displayed' become True?

A After Step 3

B After Step 5

C After Step 4

D At the start

💡 Hint

Look at the 'plot displayed' row in variable_tracker and see when it changes to True

If bbox_to_anchor was set to (0, 0), where would the legend appear relative to the plot?

A Inside the plot at the center

B Outside the plot on the top right

C Outside the plot on the bottom left

D Inside the plot at the top left

💡 Hint

bbox_to_anchor sets the anchor point; (0,0) is bottom left outside the plot area

Concept Snapshot

plt.legend() adds a legend to a plot.
Use loc to set legend position.
bbox_to_anchor moves legend outside plot.
Example: loc='center left', bbox_to_anchor=(1, 0.5) places legend right outside.
Call plt.show() to display the plot with legend.

Full Transcript

This example shows how to place a legend outside a matplotlib plot. First, two lines are plotted with labels. By default, the legend appears inside the plot at the best location. Then, using plt.legend with loc='center left' and bbox_to_anchor=(1, 0.5), the legend moves outside the plot on the right center. The plot is displayed only after plt.show() is called. Variables like legend location and plot display status change step-by-step as shown in the tables.