Saving figures to files in Matplotlib - Step-by-Step Execution

Concept Flow - Saving figures to files

Create plot with matplotlib

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Call plt.savefig(filename)

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Figure saved to file

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Optionally close figure with plt.close()

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End

First, create a plot. Then call savefig() with a filename to save the image file. Optionally close the figure to free memory.

Execution Sample

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6])
plt.savefig('myplot.png')
plt.close()

This code plots points and saves the figure as 'myplot.png' file.

Execution Table

Step	Action	Evaluation	Result
1	Import matplotlib.pyplot as plt	Module loaded	plt ready to use
2	Call plt.plot([1,2,3], [4,5,6])	Create line plot	Plot created in memory
3	Call plt.savefig('myplot.png')	Save current figure to file	File 'myplot.png' created on disk
4	Call plt.close()	Close current figure	Figure memory freed
5	End of script	No more commands	Plot saved and program ends

💡 All steps completed, figure saved and closed.

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4
plt	module loaded	plot created	figure saved	figure closed

Key Moments - 2 Insights

Why do we call plt.close() after saving the figure?

Calling plt.close() frees memory by closing the figure. Without it, figures stay in memory which can slow down programs if many plots are created. See execution_table step 4.

What happens if we call plt.savefig() before plt.plot()?

If plt.savefig() is called before creating a plot, it saves an empty figure. The plot must be created first as shown in execution_table step 2 before saving in step 3.

Visual Quiz - 3 Questions

Look at the execution table, what is the result after step 3?

A Plot created in memory

B Figure memory freed

C File 'myplot.png' created on disk

D Module loaded

💡 Hint

Check the 'Result' column for step 3 in the execution_table.

At which step is the figure closed to free memory?

A Step 2

B Step 4

C Step 3

D Step 5

💡 Hint

Look at the 'Action' column in execution_table for closing the figure.

If we skip plt.close(), what changes in variable_tracker after step 4?

A 'figure closed' would not appear

B 'figure saved' changes to 'figure closed'

C 'plot created' changes to 'figure closed'

D 'figure closed' remains the same

💡 Hint

Check variable_tracker row for 'plt' after step 4 to see if figure is closed.

Concept Snapshot

Saving figures to files with matplotlib:
1. Create plot with plt.plot()
2. Save with plt.savefig('filename.png')
3. Optionally close figure with plt.close() to free memory
4. Supported formats: PNG, JPG, PDF, SVG
5. File saved in current directory unless path given

Full Transcript

This visual execution shows how to save a matplotlib figure to a file. First, the plot is created using plt.plot(). Then plt.savefig() saves the current figure to a file named 'myplot.png'. Calling plt.close() frees memory by closing the figure. The execution table traces each step and the variable tracker shows the state of plt module. Key moments clarify why closing figures is important and the order of commands. The quiz tests understanding of saving and closing figures. The snapshot summarizes the steps to save plots as image files.