handle to/from_spec cases where there is no focus

pygridgen/grid.py

@@ -196,13 +196,18 @@ def __call__(self, x, y):
         return x, y
 
     def to_spec(self):
+        """ Export to the defining properties of the focus to a JSON-like
+        structure
+        """
         output_spec = []
         for focuspoint in self._focuspoints:
             output_spec.append(focuspoint.to_dict())
         return output_spec
 
     @classmethod
     def from_spec(cls, foci):
+        """ Create a new focus object from a JSON-like structure
+        """
         f = cls()
         for focuspoint in foci:
             f.add_focus(**focuspoint)
@@ -986,9 +991,10 @@ def generate_grid(self):
         super(Gridgen, self).__init__(x, y)
 
     def to_spec(self):
+        """ Export the grid-defining parameters into a JSON-like structure """
         output_dict = {'xbry': self.xbry, 'ybry': self.ybry,
                        'beta': self.beta, 'shape': self.shape,
-                       'focus': self.focus.to_spec(),
+                       'focus': self.focus.to_spec() if self.focus else None,
                        'ul_idx': self.ul_idx, 'proj': self.proj,
                        'nnodes': self.nnodes, 'precision': self.precision,
                        'nppe': self.nppe, 'newton': self.newton,
@@ -998,8 +1004,9 @@ def to_spec(self):
 
     @classmethod
     def from_spec(cls, attributes):
+        """ Create a new grid from a JSON-like data structure """
         focus_spec = attributes.pop('focus', None)
-        focus = Focus.from_spec(focus_spec)
+        focus = Focus.from_spec(focus_spec) if focus_spec else None
         return cls(focus=focus, **attributes)
 
 

pygridgen/tests/test_grid.py

@@ -591,14 +591,17 @@ def test_mask_poylgon(grid_and_knowns):
         nptest.assert_array_almost_equal(grid.mask_rho, known_mask_rho)
 
 
-def test_gridgen_to_from_spec():
+@pytest.mark.parametrize('use_focus', [True, False])
+def test_gridgen_to_from_spec(use_focus):
     x = numpy.array([0.50, 2.00, 2.00, 3.50, 3.50, 2.00, 2.00, 0.50, 0.50])
     y = numpy.array([0.50, 0.50, 1.75, 1.75, 2.25, 2.25, 3.50, 3.50, 0.50])
     beta = numpy.array([1, 1, -1, 1, 1, -1, 1, 1, 0])
 
-    focus = pygridgen.Focus()
-    focus.add_focus(0.50, 'y', factor=5, extent=0.25)
-    focus.add_focus(0.50, 'x', factor=5, extent=0.25)
+    focus = None
+    if use_focus:
+        focus = pygridgen.Focus()
+        focus.add_focus(0.50, 'y', factor=5, extent=0.25)
+        focus.add_focus(0.50, 'x', factor=5, extent=0.25)
 
     grid1 = pygridgen.Gridgen(x, y, beta, shape=(20, 10), focus=focus)
     grid2 = pygridgen.grid.Gridgen.from_spec((grid1.to_spec()))