Save a Plot to a File in Matplotlib (using 14 formats)

The Matplotlib is a popular plotting library for Python. It can be used in Python scripts and Jupyter Notebooks. The plot can be displayed in a separate window or a notebook. What if you would like to save the plot to a file? In this article, I will show you how to save the Matplotlib plot into a file. It can be done by using 14 different formats.

Quick code snippet

Below is a quick Python code snippet that shows how to save a figure to a file.

import matplotlib.pyplot as plt

# create a plot
plt.plot([4,2,3,1,5])

# save figure
plt.savefig("my_plot.png")

Important:

1. Please call plt.show() after plt.savefig(). Otherwise, you will get an empty plot in the file.
2. For Jupyter Notebook users, you need to call plt.savefig() in the same cell in which the plot is created. Otherwise, the file has an empty figure.

The savefig function - deep dive

All plots created with Matplotlib are saved with savefig function. Please take a while a look into savefig documentation.

Below are savefig arguments that you might find useful:

• fname - a path where to save a plot. It can be without extension. For fname with the extension included the format will be automatically selected. Common extensions: .png, .pdf, .svg;
• dpi - a numeric value for dots per inch; it controls the size of the figure in pixels. You can read more in an article on how to change figure size in Matplotlib;
• bbox_inches - controls the white space around the figure, if you don't need margins, please set this parameter to tight;
• transparent - is a boolean value that can turn the plot background into transparent;
• format - is a string with the output file format. Common formats are png, pdf, svg. If not specified, it is automatically set from the fname extension. The default is png.

You can list all available formats in Matplotlib with below Python code:

import matplotlib.pyplot as plt
print(plt.gcf().canvas.get_supported_filetypes())

Output:

{
 'eps': 'Encapsulated Postscript',
 'jpg': 'Joint Photographic Experts Group',
 'jpeg': 'Joint Photographic Experts Group',
 'pdf': 'Portable Document Format',
 'pgf': 'PGF code for LaTeX',
 'png': 'Portable Network Graphics',
 'ps': 'Postscript',
 'raw': 'Raw RGBA bitmap',
 'rgba': 'Raw RGBA bitmap',
 'svg': 'Scalable Vector Graphics',
 'svgz': 'Scalable Vector Graphics',
 'tif': 'Tagged Image File Format',
 'tiff': 'Tagged Image File Format'
}

There are, in total 13 formats supported by Matplotlib.

Example of advanced save

Let's try to save a figure to PNG format with transparent background with a size of 1200x800 pixels:

import matplotlib.pyplot as plt
plt.figure(figsize=(6,4), dpi=200)
plt.plot([4,2,3,1,5])
plt.savefig("my_plot.png", transparent=True)

We set the size of the figure during creation, the size in pixels is computed by multiplying figsize by dpi.

Save Matplotlib figure

Earlier, we save plots in graphics formats. What if we would like to save the whole Matplotlib figure for further manipulation? It is possible. We can use the pickle library. It is a Python object serialization package. It doesn't need to be installed additionally.

Here is an example Python code that creates the Matplitlib figure, saves to a file, and loads it back:

import pickle 
import matplotlib.pyplot as plt

# create figure
fig = plt.figure()
plt.plot([4,2,3,1,5])

# save whole figure 
pickle.dump(fig, open("figure.pickle", "wb"))

# load figure from file
fig = pickle.load(open("figure.pickle", "rb"))

Summary

You can save the Matplotlib plot to a file using 13 graphics formats. The most common formats are .png, .pdf, .svg and .jpg. The savefig() function has useful arguments: transparent, bbox_inches, or format. There is an option to serialize the figure object to a file and load it back with the pickle package. It can be used to save the figure for future manipulations.