partial class Examples
{
  public static Rhino.Commands.Result AddCircle(Rhino.RhinoDoc doc)
  {
    Rhino.Geometry.Point3d center = new Rhino.Geometry.Point3d(0, 0, 0);
    const double radius = 10.0;
    Rhino.Geometry.Circle c = new Rhino.Geometry.Circle(center, radius);
    if (doc.Objects.AddCircle(c) != Guid.Empty)
    {
      doc.Views.Redraw();
      return Rhino.Commands.Result.Success;
    }
    return Rhino.Commands.Result.Failure;
  }
}

import Rhino
import scriptcontext
from System import Guid

def AddCircle():
    center = Rhino.Geometry.Point3d(0, 0, 0)
    radius = 10.0
    c = Rhino.Geometry.Circle(center, radius)
    if scriptcontext.doc.Objects.AddCircle(c)!= Guid.Empty:
        scriptcontext.doc.Views.Redraw()
        return Rhino.Commands.Result.Success
    return Rhino.Commands.Result.Failure

if __name__=="__main__":
    AddCircle()