Save plot to image file instead of displaying it using Matplotlib

The solution is:

pylab.savefig('foo.png')

As others have said, plt.savefig() or fig1.savefig() is indeed the way to save an image.

However I've found that in certain cases the figure is always shown. (eg. with Spyder having plt.ion(): interactive mode = On.) I work around this by forcing the closing of the figure window in my giant loop with plt.close(figure_object) (see documentation), so I don't have a million open figures during the loop:

import matplotlib.pyplot as plt
fig, ax = plt.subplots( nrows=1, ncols=1 )  # create figure & 1 axis
ax.plot([0,1,2], [10,20,3])
fig.savefig('path/to/save/image/to.png')   # save the figure to file
plt.close(fig)    # close the figure window

You should be able to re-open the figure later if needed to with fig.show() (didn't test myself).

When using matplotlib.pyplot.savefig, the file format can be specified by the extension:

from matplotlib import pyplot as plt

plt.savefig('foo.png')
plt.savefig('foo.pdf')

That gives a rasterized or vectorized output respectively. In addition, there is sometimes undesirable whitespace around the image, which can be removed with:

plt.savefig('foo.png', bbox_inches='tight')

Note that if showing the plot, plt.show() should follow plt.savefig(); otherwise, the file image will be blank.