Add input check to secondary axes

ZachDaChampion · ZachDaChampion · commit 5f0b714d3198 · 2023-04-04T12:46:08.000-04:00
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -582,14 +582,17 @@ def invert(x):
             secax.set_xlabel('Period [s]')
             plt.show()
         """
-        if location in ['top', 'bottom'] or isinstance(location, Real):
-            secondary_ax = SecondaryAxis(self, 'x', location, functions,
-                                         transform, **kwargs)
-            self.add_child_axes(secondary_ax)
-            return secondary_ax
-        else:
+        if not (location in ['top', 'bottom'] or isinstance(location, Real)):
             raise ValueError('secondary_xaxis location must be either '
                              'a float or "top"/"bottom"')
+        if not (isinstance(transform, mtransforms.Transform) or transform is None):
+            raise ValueError('transform must be either an mtransforms.Transform '
+                             'or None')
+
+        secondary_ax = SecondaryAxis(self, 'x', location, functions,
+                                        transform, **kwargs)
+        self.add_child_axes(secondary_ax)
+        return secondary_ax
 
     @_docstring.dedent_interpd
     def secondary_yaxis(self, location, *, functions=None, transform=None, **kwargs):
@@ -614,14 +617,16 @@ def secondary_yaxis(self, location, *, functions=None, transform=None, **kwargs)
                                                            np.rad2deg))
             secax.set_ylabel('radians')
         """
-        if location in ['left', 'right'] or isinstance(location, Real):
-            secondary_ax = SecondaryAxis(self, 'y', location, functions,
-                                         transform, **kwargs)
-            self.add_child_axes(secondary_ax)
-            return secondary_ax
-        else:
-            raise ValueError('secondary_yaxis location must be either '
+        if not (location in ['left', 'right'] or isinstance(location, Real)):
+            raise ValueError('secondary_xaxis location must be either '
                              'a float or "left"/"right"')
+        if not (isinstance(transform, mtransforms.Transform) or transform is None):
+            raise ValueError('transform must be either an mtransforms.Transform '
+                             'or None')
+        secondary_ax = SecondaryAxis(self, 'y', location, functions,
+                                        transform, **kwargs)
+        self.add_child_axes(secondary_ax)
+        return secondary_ax
 
     @_docstring.dedent_interpd
     def text(self, x, y, s, fontdict=None, **kwargs):
