Add to_box_params method for exporting boxes to GSD

freud/box.py

@@ -639,6 +639,24 @@ def to_matrix(self):
             ]
         )
 
+    def to_box_params(self):
+        r"""Returns the box lengths and tilt factors as a flat (6,) tuple.
+
+        The output from this method can be saved as a `GSD box <https://gsd.readthedocs.io/en/stable/schema-hoomd.html#chunk-configuration-box>`_.
+
+        Example::
+
+            >>> box = freud.box.Box.cube(L=10)
+            >>> box.to_box_params()
+            (10.0, 10.0, 10.0, 0.0, 0.0, 0.0)
+
+        Returns:
+            tuple:
+                The box extents along each axis and tilt factors
+                :math:`(L_x, L_y, L_z, xy, xz, yz)`.
+        """
+        return (self.Lx, self.Ly, self.Lz, self.xy, self.xz, self.yz)
+
     def to_box_lengths_and_angles(self):
         r"""Return the box lengths and angles.
 

tests/test_box_box.py

@@ -450,6 +450,16 @@ def test_to_dict(self):
         for k, v in box_dict.items():
             npt.assert_allclose(v, box2[k])
 
+    def test_to_box_params(self):
+        box = freud.box.Box(2, 2, 2, 1, 0.5, 0.1)
+        npt.assert_equal(box.to_box_params(), [*box.to_dict().values()][:6])
+        npt.assert_equal(
+            box.to_box_params(), [box.Lx, box.Ly, box.Lz, box.xy, box.xz, box.yz]
+        )
+
+        box2 = freud.box.Box.cube(0.001)
+        npt.assert_allclose(box2.to_box_params(), [0.001, 0.001, 0.001, 0, 0, 0])
+
     def test_from_box(self):
         """Test various methods of initializing a box"""
         box = freud.box.Box(2, 2, 2, 1, 0.5, 0.1)