import cadquery as cq
w0=cq.Workplane('XY',origin=(0,0,50))
r=w0.workplane(offset=-100/2).box(10,18,100).union(w0.sketch().segment((-12,5),(-10,5)).segment((-10,-17)).segment((12,-17)).segment((12,17)).segment((-12,17)).close().assemble().push([(2,-5)]).circle(9,mode='s').finalize().extrude(-95))