python – how to get the data from an plt.imshow()?

a should be a matplotlib.image.AxesImage instance, in which case you can use

a.get_array() 

and

a.set_array(data)

The array is stored as a masked array.

Example

There’s an official example available at http://matplotlib.org/examples/animation/dynamic_image.html.

Direct access

You can also use

a._A

to access the array data directly, though I imagine that the getters and setters are the preferred method.