can someone advise on how to make simple venn diagrams, like the one here:

http://en.wikipedia.org/wiki/File:Venn_diagram_cmyk.svg

simply three (or more) intersecting circles, such that one can label every point of their intersection, and maybe make the circles in size proportion to the number of elements they are supposed to represent. i know some people use Sage for this but i prefer to use matplotlib directly.

any help / info on how to get started on this or some example code would be greatly appreciated.

thank you.