matplotlib
diff --git a/‎doc/api/next_api_changes/2018-12-16-TH-deprecations.rst
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+10Lines changed: 10 additions & 0 deletions b/‎doc/api/next_api_changes/2018-12-16-TH-deprecations.rst
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+10Lines changed: 10 additions & 0 deletions
diff --git a/‎lib/matplotlib/ticker.py
Copy file name to clipboardExpand all lines: lib/matplotlib/ticker.py
+36-14Lines changed: 36 additions & 14 deletions b/‎lib/matplotlib/ticker.py
Copy file name to clipboardExpand all lines: lib/matplotlib/ticker.py
+36-14Lines changed: 36 additions & 14 deletions
@@ -0,0 +1,10 @@
+Deprecations
+````````````
+
+The class variable ``matplotlib.ticker.MaxNLocator.default_params`` is
+deprecated and will be removed in a future version. The defaults are not
+supposed to be user-configurable.
+
+``matplotlib.ticker.MaxNLocator`` and its ``set_params`` method will issue
+a warning on unknown keyword arguments instead of silently ignoring them.
+Future versions will raise an error.
@@ -1824,12 +1824,12 @@ class MaxNLocator(Locator):
     """
     Select no more than N intervals at nice locations.
     """
-    default_params = dict(nbins=10,
-                          steps=None,
-                          integer=False,
-                          symmetric=False,
-                          prune=None,
-                          min_n_ticks=2)
+    _default_params = dict(nbins=10,
+                           steps=None,
+                           integer=False,
+                           symmetric=False,
+                           prune=None,
+                           min_n_ticks=2)
 
     def __init__(self, *args, **kwargs):
         """
@@ -1873,12 +1873,17 @@ def __init__(self, *args, **kwargs):
 
         """
         if args:
+            if 'nbins' in kwargs:
+                cbook.deprecated("3.1",
+                                 message='Calling MaxNLocator with positional '
+                                         'and keyword parameter *nbins* is '
+                                         'considered an error and will fail '
+                                         'in future versions of matplotlib.')
             kwargs['nbins'] = args[0]
             if len(args) > 1:
                 raise ValueError(
                     "Keywords are required for all arguments except 'nbins'")
-        self.set_params(**self.default_params)
-        self.set_params(**kwargs)
+        self.set_params(**{**self._default_params, **kwargs})
 
     @staticmethod
     def _validate_steps(steps):
@@ -1895,6 +1900,16 @@ def _validate_steps(steps):
             steps = np.hstack((steps, 10))
         return steps
 
+    @cbook.deprecated("3.1")
+    @property
+    def default_params(self):
+        return self._default_params
+
+    @cbook.deprecated("3.1")
+    @default_params.setter
+    def default_params(self, params):
+        self._default_params = params
+
     @staticmethod
     def _staircase(steps):
         # Make an extended staircase within which the needed
@@ -1906,28 +1921,35 @@ def _staircase(steps):
     def set_params(self, **kwargs):
         """Set parameters within this locator."""
         if 'nbins' in kwargs:
-            self._nbins = kwargs['nbins']
+            self._nbins = kwargs.pop('nbins')
             if self._nbins != 'auto':
                 self._nbins = int(self._nbins)
         if 'symmetric' in kwargs:
-            self._symmetric = kwargs['symmetric']
+            self._symmetric = kwargs.pop('symmetric')
         if 'prune' in kwargs:
-            prune = kwargs['prune']
+            prune = kwargs.pop('prune')
             if prune is not None and prune not in ['upper', 'lower', 'both']:
                 raise ValueError(
                     "prune must be 'upper', 'lower', 'both', or None")
             self._prune = prune
         if 'min_n_ticks' in kwargs:
-            self._min_n_ticks = max(1, kwargs['min_n_ticks'])
+            self._min_n_ticks = max(1, kwargs.pop('min_n_ticks'))
         if 'steps' in kwargs:
-            steps = kwargs['steps']
+            steps = kwargs.pop('steps')
             if steps is None:
                 self._steps = np.array([1, 1.5, 2, 2.5, 3, 4, 5, 6, 8, 10])
             else:
                 self._steps = self._validate_steps(steps)
             self._extended_steps = self._staircase(self._steps)
         if 'integer' in kwargs:
-            self._integer = kwargs['integer']
+            self._integer = kwargs.pop('integer')
+        if kwargs:
+            param = next(k for k in kwargs)
+            cbook.warn_deprecated("3.1",
+                                  message="MaxNLocator.set_params got an "
+                                          f"unexpected parameter: {param}")
+
+
 
     def _raw_ticks(self, vmin, vmax):
         """