An edge shared by two faces is one edge. A box has twelve. A cylinder has three: its two circles and the seam where its curved face closes on itself, which bounds that face but is not a feature of the part.

 numedges (solid.box (10, 20, 30))
 ⇒ 12
 numedges (solid.cylinder (5, 10))
 ⇒ 3

See also: solid.Shape.numsolids, solid.Shape.numfaces

Source Code: solid.Shape