How to export plots from matplotlib with transparent background?

I am using matplotlib to make some graphs and unfortunately I cannot export them without the white background.

sample plot with solid white background

In other words, when I export a plot like this and position it on top of another image, the white background hides what is behind it rather than allowing it to show through. How can I export plots with a transparent background instead?

Use the matplotlib savefig function with the keyword argument transparent=True to save the image as a png file.

    In [30]: x = np.linspace(0,6,31)

    In [31]: y = np.exp(-0.5*x) * np.sin(x)

    In [32]: plot(x, y, 'bo-')
    Out[32]: [<matplotlib.lines.Line2D at 0x3f29750>]            

    In [33]: savefig('demo.png', transparent=True)

Result: demo.png

Of course, that plot doesn't demonstrate the transparency. Here's a screenshot of the PNG file displayed using the ImageMagick display command. The checkerboard pattern is the background that is visible through the transparent parts of the PNG file.

display screenshot

From: stackoverflow.com/q/15857647

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