While it’s technically true that a circle is also a member of the arc family, having rs.IsArc return True with a circle object doesn’t help us much, especially since we have rs.IsArc as well… It means to get only arcs and not circles, you need to have
if rs.IsArc(obj) and not rs.IsCircle(obj)
Note also that vb Rhinoscript Rhino.IsArc(obj)
does not return True if the object is a circle. I would prefer that Python rhinoscriptsyntax rs.IsArc behave the same way; if I want to include both arcs and circles I can always use rs.IsArc(obj) or rs.IsCircle(obj)
Thx,
–Mitch