[NOTE: copied from another branch for easy reading for others] A saner map/filter/product version: map(lambda (w,s,l): {'widget': w, 'sprocket': s, 'locat

[NOTE: copied from another branch for easy reading for others] A saner map/filter/product version: map(lambda (w,s,l): {'widget': w, 'sprocket': s, 'location': l} filter(lambda (w,s,l): l.hasInStock(w) and l.hasInStock(s) and w.isUsableWith(s), product(widgets, sprockets, locations)))