toggle matcap library through python?

is it possible to toggle the matcap library?

I know the toolshelf can be toggled. There must be a way, if not, please correct me.

import bpy

for window in
    screen = window.screen

    for area in screen.areas:
        if area.type == 'VIEW_3D':
            area.spaces[0].use_matcap = True
            area.spaces[0].matcap_icon = '19'

Thanks for this useful script, but i would like to actually open the library rather than choosing a matcap.