Added sort_by lambda Issue#485

src/build123d/topology/shape_core.py

@@ -2624,7 +2624,9 @@ class ShapeList(list[T]):
         return ShapeList([s for shape in self for s in shape.solids()])  # type: ignore
 
     def sort_by(
-        self, sort_by: Axis | Edge | Wire | SortBy = Axis.Z, reverse: bool = False
+        self,
+        sort_by: Axis | Callable[[T], K] | Edge | Wire | SortBy = Axis.Z,
+        reverse: bool = False,
     ) -> ShapeList[T]:
         """sort by
 
@@ -2639,7 +2641,11 @@ class ShapeList(list[T]):
             ShapeList: sorted list of objects
         """
 
-        if isinstance(sort_by, Axis):
+        if callable(sort_by):
+            # If a callable is provided, use it directly as the key
+            objects = sorted(self, key=sort_by, reverse=reverse)
+
+        elif isinstance(sort_by, Axis):
             if sort_by.wrapped is None:
                 raise ValueError("Cannot sort by an empty axis")
             assert sort_by.location is not None
@@ -2702,6 +2708,8 @@ class ShapeList(list[T]):
                     key=lambda obj: obj.volume,  # type: ignore
                     reverse=reverse,
                 )
+        else:
+            raise ValueError("Invalid sort_by criteria provided")
 
         return ShapeList(objects)
 

tests/test_direct_api/test_shape_list.py

@@ -79,6 +79,20 @@ class TestShapeList(unittest.TestCase):
         faces = Solid.make_box(1, 2, 3).faces() < SortBy.AREA
         self.assertAlmostEqual(faces[-1].area, 2, 5)
 
+    def test_sort_by_lambda(self):
+        c = Solid.make_cone(2, 1, 2)
+        flat_faces = c.faces().filter_by(GeomType.PLANE)
+        sorted_flat_faces = flat_faces.sort_by(lambda f: f.area)
+        smallest = sorted_flat_faces[0]
+        largest = sorted_flat_faces[-1]
+
+        self.assertAlmostEqual(smallest.area, math.pi * 1**2, 5)
+        self.assertAlmostEqual(largest.area, math.pi * 2**2, 5)
+
+    def test_sort_by_invalid(self):
+        with self.assertRaises(ValueError):
+            Solid.make_box(1, 1, 1).faces().sort_by(">Z")
+
     def test_filter_by_geomtype(self):
         non_planar_faces = (
             Solid.make_cylinder(1, 1).faces().filter_by(GeomType.PLANE, reverse=True)