what is unit of the parameter of “radius” in matplotlib.patches.Circle and matplotlib.patches.CirclePolygon
Pixel? point? centmeter?
It depends on the transform attached to the Artist. See https://matplotlib.org/3.1.1/tutorials/advanced/transforms_tutorial.html for more details, but the very short version is that we have tools to transform from whatever coordinate system the input is to “screen space” which ends up being either pixels or inches depending on the output.
When you do ax.add_artist(circ) if the transform is not explicitly set, it will be set to the data transform so the units of the location and radius will be in data-space.
What is your application?