How do you create a "donut hole" / cut-out-effect using folium?

Question

I've tried adjusting parameters and changing the order in which these circles are added. I can't get the interior circle, or "hole", to remain transparent. The outer circle always predominates.

m = folium.Map(tiles="cartodbpositron", location=xy, zoom_start=14, attr="CartoDB")

folium.Circle(xy, radius=1800, fill=True, fill_opacity=.5, fill_color='black').add_to(m)
folium.Circle(xy, radius=1000, fill=False, fill_opacity=0, fill_color=None).add_to(m)

m

In effect, I'm trying to do what Shapely does:

donut = Point(0, 0).buffer(2.0).difference(Point(0, 0).buffer(1.0))

But I want to do it with Folium because projecting a circle made with Shapely yields an object that's rough, even elliptical.

Answer 1

You can unfortunately not do this that way, with two circles on top of each other. A Circle element with a hole in it should be drawn as a polygon with a hole in it.

You should use what you did:

donut = Point(0, 0).buffer(2.0).difference(Point(0, 0).buffer(1.0))

In order to have it shown not as an elliptical geometry, you should take care of using projected coordinates instead of geographical coordinates. This can be done with (for example) geopandas. See this example.