Merge pull request matplotlib#24749 from chahak13/24743_contour_kwargs

Support only positional args in contour. Error if no positional argument.

Author: ksunden

lib/matplotlib/contour.py

@@ -1381,7 +1381,7 @@ def _process_args(self, *args, corner_mask=None, algorithm=None, **kwargs):
         """
         Process args and kwargs.
         """
-        if isinstance(args[0], QuadContourSet):
+        if args and isinstance(args[0], QuadContourSet):
             if self.levels is None:
                 self.levels = args[0].levels
             self.zmin = args[0].zmin
@@ -1441,13 +1441,15 @@ def _contour_args(self, args, kwargs):
         else:
             fn = 'contour'
         nargs = len(args)
-        if nargs <= 2:
+
+        if 0 < nargs <= 2:
             z, *args = args
             z = ma.asarray(z)
             x, y = self._initialize_x_y(z)
-        elif nargs <= 4:
+        elif 2 < nargs <= 4:
             x, y, z_orig, *args = args
             x, y, z = self._check_xyz(x, y, z_orig, kwargs)
+
         else:
             raise _api.nargs_error(fn, takes="from 1 to 4", given=nargs)
         z = ma.masked_invalid(z, copy=False)

lib/matplotlib/tests/test_contour.py

@@ -693,6 +693,13 @@ def test_contour_remove():
     assert ax.get_children() == orig_children
 
 
+def test_contour_no_args():
+    fig, ax = plt.subplots()
+    data = [[0, 1], [1, 0]]
+    with pytest.raises(TypeError, match=r"contour\(\) takes from 1 to 4"):
+        ax.contour(Z=data)
+
+
 def test_bool_autolevel():
     x, y = np.random.rand(2, 9)
     z = (np.arange(9) % 2).reshape((3, 3)).astype(bool)