Memory management with large figures in Matplotlib

Introduction

Large figures can use a lot of computer memory. Managing memory well helps your computer run smoothly and avoids crashes.

When creating big or many plots in a loop.

When working with high-resolution images or detailed charts.

When running data analysis scripts that generate multiple figures.

When your computer slows down or runs out of memory during plotting.

When saving many figures to files in one program run.

Syntax

Matplotlib

import matplotlib.pyplot as plt

# Create a figure
fig, ax = plt.subplots()

# Plot your data
ax.plot(data)

# Show or save the figure
plt.show()  # or plt.savefig('file.png')

# Clear the figure to free memory
plt.close(fig)

Use plt.close() to free memory after you finish with a figure.

Closing figures is important when making many plots in a loop.

Examples

This example creates and shows 3 plots one by one, closing each to save memory.

Matplotlib

import matplotlib.pyplot as plt

for i in range(3):
    fig, ax = plt.subplots()
    ax.plot([1, 2, 3], [i, i*2, i*3])
    plt.show()
    plt.close(fig)

Here, the figure is saved to a file and then closed to free memory.

Matplotlib

import matplotlib.pyplot as plt

fig, ax = plt.subplots()
ax.plot([1, 2, 3], [4, 5, 6])
plt.savefig('myplot.png')
plt.close(fig)

Sample Program

This program makes a large plot with 100,000 points, shows it, then closes the figure to free memory.

Matplotlib

import matplotlib.pyplot as plt
import numpy as np

# Create large data
x = np.linspace(0, 100, 100000)
y = np.sin(x)

# Create a large figure
fig, ax = plt.subplots(figsize=(10, 6))
ax.plot(x, y)
ax.set_title('Large Figure Example')

# Show the figure
plt.show()

# Close the figure to free memory
plt.close(fig)

# Print confirmation
print('Figure created and closed to manage memory.')

Important Notes

Always close figures you no longer need to avoid using too much memory.

Using plt.close() is especially important in loops or long scripts.

If you forget to close figures, your program might slow down or crash.

Summary

Large figures use a lot of memory and can slow your computer.

Use plt.close() to free memory after showing or saving a figure.

Closing figures is very important when making many plots in one program.