matplotlib · tacaswell · Mar 1, 2023 · Feb 27, 2023
diff --git a/doc/api/next_api_changes/deprecations/25352-GL.rst b/doc/api/next_api_changes/deprecations/25352-GL.rst
@@ -0,0 +1,4 @@
+``Grouper.clean()``
+~~~~~~~~~~~~~~~~~~~
+
+with no replacement. The Grouper class now cleans itself up automatically.
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -1363,8 +1363,6 @@ def __clear(self):
         self.xaxis.set_clip_path(self.patch)
         self.yaxis.set_clip_path(self.patch)
 
-        self._shared_axes["x"].clean()
-        self._shared_axes["y"].clean()
         if self._sharex is not None:
             self.xaxis.set_visible(xaxis_visible)
             self.patch.set_visible(patch_visible)

diff --git a/lib/matplotlib/cbook.py b/lib/matplotlib/cbook.py
@@ -786,78 +786,68 @@ class Grouper:
     """
 
     def __init__(self, init=()):
-        self._mapping = {weakref.ref(x): [weakref.ref(x)] for x in init}
+        self._mapping = weakref.WeakKeyDictionary(
+            {x: weakref.WeakSet([x]) for x in init})
 
     def __getstate__(self):
         return {
             **vars(self),
             # Convert weak refs to strong ones.
-            "_mapping": {k(): [v() for v in vs] for k, vs in self._mapping.items()},
+            "_mapping": {k: set(v) for k, v in self._mapping.items()},
         }
 
     def __setstate__(self, state):
         vars(self).update(state)
         # Convert strong refs to weak ones.
-        self._mapping = {weakref.ref(k): [*map(weakref.ref, vs)]
-                         for k, vs in self._mapping.items()}
+        self._mapping = weakref.WeakKeyDictionary(
+            {k: weakref.WeakSet(v) for k, v in self._mapping.items()})
 
     def __contains__(self, item):
-        return weakref.ref(item) in self._mapping
+        return item in self._mapping
 
+    @_api.deprecated("3.8", alternative="none, you no longer need to clean a Grouper")
     def clean(self):
         """Clean dead weak references from the dictionary."""
-        mapping = self._mapping
-        to_drop = [key for key in mapping if key() is None]
-        for key in to_drop:
-            val = mapping.pop(key)
-            val.remove(key)
 
     def join(self, a, *args):
         """
         Join given arguments into the same set.  Accepts one or more arguments.
         """
         mapping = self._mapping
-        set_a = mapping.setdefault(weakref.ref(a), [weakref.ref(a)])
+        set_a = mapping.setdefault(a, weakref.WeakSet([a]))
 
         for arg in args:
-            set_b = mapping.get(weakref.ref(arg), [weakref.ref(arg)])
+            set_b = mapping.get(arg, weakref.WeakSet([arg]))
             if set_b is not set_a:
                 if len(set_b) > len(set_a):
                     set_a, set_b = set_b, set_a
-                set_a.extend(set_b)
+                set_a.update(set_b)
                 for elem in set_b:
                     mapping[elem] = set_a
 
-        self.clean()
-
     def joined(self, a, b):
         """Return whether *a* and *b* are members of the same set."""
-        self.clean()
-        return (self._mapping.get(weakref.ref(a), object())
-                is self._mapping.get(weakref.ref(b)))
+        return (self._mapping.get(a, object()) is self._mapping.get(b))
 
     def remove(self, a):
-        self.clean()
-        set_a = self._mapping.pop(weakref.ref(a), None)
+        set_a = self._mapping.pop(a, None)
         if set_a:
-            set_a.remove(weakref.ref(a))
+            set_a.remove(a)
 
     def __iter__(self):
         """
         Iterate over each of the disjoint sets as a list.
 
         The iterator is invalid if interleaved with calls to join().
         """
-        self.clean()
         unique_groups = {id(group): group for group in self._mapping.values()}
         for group in unique_groups.values():
-            yield [x() for x in group]
+            yield [x for x in group]
 
     def get_siblings(self, a):
         """Return all of the items joined with *a*, including itself."""
-        self.clean()
-        siblings = self._mapping.get(weakref.ref(a), [weakref.ref(a)])
-        return [x() for x in siblings]
+        siblings = self._mapping.get(a, [a])
+        return [x for x in siblings]
 
 
 class GrouperView:

diff --git a/lib/matplotlib/tests/test_cbook.py b/lib/matplotlib/tests/test_cbook.py
@@ -1,7 +1,6 @@
 import itertools
 import pickle
 
-from weakref import ref
 from unittest.mock import patch, Mock
 
 from datetime import datetime, date, timedelta
@@ -590,11 +589,11 @@ class Dummy:
     mapping = g._mapping
 
     for o in objs:
-        assert ref(o) in mapping
+        assert o in mapping
 
-    base_set = mapping[ref(objs[0])]
+    base_set = mapping[objs[0]]
     for o in objs[1:]:
-        assert mapping[ref(o)] is base_set
+        assert mapping[o] is base_set
 
 
 def test_flatiter():

diff --git a/lib/mpl_toolkits/mplot3d/axes3d.py b/lib/mpl_toolkits/mplot3d/axes3d.py
@@ -640,7 +640,6 @@ def autoscale_view(self, tight=None, scalex=True, scaley=True,
             _tight = self._tight = bool(tight)
 
         if scalex and self.get_autoscalex_on():
-            self._shared_axes["x"].clean()
             x0, x1 = self.xy_dataLim.intervalx
             xlocator = self.xaxis.get_major_locator()
             x0, x1 = xlocator.nonsingular(x0, x1)
@@ -653,7 +652,6 @@ def autoscale_view(self, tight=None, scalex=True, scaley=True,
             self.set_xbound(x0, x1)
 
         if scaley and self.get_autoscaley_on():
-            self._shared_axes["y"].clean()
             y0, y1 = self.xy_dataLim.intervaly
             ylocator = self.yaxis.get_major_locator()
             y0, y1 = ylocator.nonsingular(y0, y1)
@@ -666,7 +664,6 @@ def autoscale_view(self, tight=None, scalex=True, scaley=True,
             self.set_ybound(y0, y1)
 
         if scalez and self.get_autoscalez_on():
-            self._shared_axes["z"].clean()
             z0, z1 = self.zz_dataLim.intervalx
             zlocator = self.zaxis.get_major_locator()
             z0, z1 = zlocator.nonsingular(z0, z1)