Saving figures in Data Analysis Python - Step-by-Step Execution

Concept Flow - Saving figures

Create plot with data

↓

Call save function

↓

Specify filename and format

↓

File saved to disk

↓

Check file exists

↓

Done

This flow shows how a figure is created, saved to a file, and then confirmed saved.

Execution Sample

Data Analysis Python

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

This code creates a simple line plot and saves it as 'myplot.png' in the current folder.

Execution Table

Step	Action	Input/Parameters	Result/Output
1	Import matplotlib.pyplot	None	Module loaded as plt
2	Create plot	x=[1,2,3], y=[4,5,6]	Plot object created with line
3	Save figure	Filename='myplot.png'	File 'myplot.png' written to disk
4	Close plot	None	Plot resources freed
5	Check file	Filename='myplot.png'	File exists on disk

💡 All steps completed, figure saved successfully

Variable Tracker

Variable	Start	After Step 2	After Step 3	After Step 4	Final
plt	module loaded	plot created	file saved	plot closed	plot closed
filename	None	None	'myplot.png'	'myplot.png'	'myplot.png'

Key Moments - 2 Insights

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

plt.close() frees memory and closes the figure window. Without it, plots may accumulate in memory. See execution_table step 4.

What happens if we save the figure before plotting?

Saving before plotting writes an empty or blank file. The plot must be created first. See execution_table step 2 then 3.

Visual Quiz - 3 Questions

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

A Plot object created

B File 'myplot.png' written to disk

C Plot resources freed

D Module loaded as plt

💡 Hint

Check the 'Result/Output' column for step 3 in execution_table

At which step is the plot closed to free resources?

A Step 4

B Step 2

C Step 3

D Step 5

💡 Hint

Look at the 'Action' column in execution_table for when plt.close() is called

If we change the filename to 'plot.pdf', what changes in the execution table?

A Step 4 is skipped

B Step 2 action changes to create PDF plot

C Step 3 result changes to 'File plot.pdf written to disk'

D No changes at all

💡 Hint

Filename is used in step 3 for saving the file, see execution_table step 3

Concept Snapshot

Saving figures in Python with matplotlib:
1. Create plot with plt.plot()
2. Save with plt.savefig('filename.ext')
3. Close plot with plt.close() to free memory
Supports formats like PNG, PDF, SVG
Always save after plotting, before closing

Full Transcript

This lesson shows how to save figures using matplotlib in Python. First, we import matplotlib.pyplot as plt. Then we create a plot using plt.plot() with data points. Next, we save the figure to a file using plt.savefig() and specify the filename and format. After saving, we call plt.close() to free memory and close the plot. Finally, we can check that the file exists on disk. This process ensures the figure is saved correctly and resources are managed well.