Saving plots to a file

Saving a plot to a file is an easy task. The following example shows how:

In [1]: import matplotlib.pyplot as plt
In [2]: plt.plot([1, 2, 3])
Out[2]: [<matplotlib.lines.Line2D object at 0x22a2f10>]
In [3]: plt.savefig('plot123.png')

Just a call to savefig() with the filename as the parameter, and we can find the saved plot in the current directory.

$ file plot123.png
plot123.png: PNG image, 800 x 600, 8-bit/color RGBA, non-interlaced

The file format is based on the filename extension (so in the previous example, we saved a PNG image).

Two values govern the resulting image size in pixels—the figure size and the DPI.

Here, we can see the default values for Matplotlib:

In [1]: import matplotlib as mpl
In [2]: mpl.rcParams['figure.figsize']
Out[2]: [8.0, 6.0]
In [3]: mpl.rcParams['savefig.dpi']
Out[3]: 100

So, an 8x6 inches figure with 100 DPI results in an 800x600 pixels image (as seen in the previous example).

When an image is displayed on the screen, the length units...