matplotlib · anntzer · Mar 3, 2018
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -395,15 +395,16 @@ def _grab_next_args(self, *args, **kwargs):
             yield from self._plot_args(this, kwargs)
 
 
+_shared_x_axes = cbook.Grouper()
+_shared_y_axes = cbook.Grouper()
+_twinned_axes = cbook.Grouper()
+
+
 class _AxesBase(martist.Artist):
     """
     """
     name = "rectilinear"
 
-    _shared_x_axes = cbook.Grouper()
-    _shared_y_axes = cbook.Grouper()
-    _twinned_axes = cbook.Grouper()
-
     def __str__(self):
         return "{0}({1[0]:g},{1[1]:g};{1[2]:g}x{1[3]:g})".format(
             type(self).__name__, self._position.bounds)
@@ -468,6 +469,13 @@ def __init__(self, fig, rect,
         """ % {'scale': ' | '.join(
             [repr(x) for x in mscale.get_scale_names()])}
         martist.Artist.__init__(self)
+
+        # Reference the global instances in the instance dict to support
+        # pickling.
+        self._shared_x_axes = _shared_x_axes
+        self._shared_y_axes = _shared_y_axes
+        self._twinned_axes = _twinned_axes
+
         if isinstance(rect, mtransforms.Bbox):
             self._position = rect
         else:

diff --git a/lib/matplotlib/cbook/__init__.py b/lib/matplotlib/cbook/__init__.py
@@ -981,6 +981,25 @@ class Grouper(object):
     def __init__(self, init=()):
         self._mapping = {ref(x): [ref(x)] for x in init}
 
+    def __getstate__(self):
+        mapping = {}
+        for k, vs in self._mapping.items():
+            k = k()
+            if k is None:
+                continue
+            mapping[k] = l = []
+            for v in vs:
+                v = v()
+                if v is None:
+                    continue
+                l.append(v)
+        return {"_mapping": mapping}
+
+    def __setstate__(self, state):
+        self.__dict__ = state
+        self._mapping = {ref(k): [ref(v) for v in vs]
+                         for k, vs in self._mapping.items()}
+
     def __contains__(self, item):
         return ref(item) in self._mapping
 

diff --git a/lib/matplotlib/tests/test_pickle.py b/lib/matplotlib/tests/test_pickle.py
@@ -187,3 +187,10 @@ def test_rrulewrapper():
     except RecursionError:
         print('rrulewrapper pickling test failed')
         raise
+
+
+def test_shared():
+    fig, axs = plt.subplots(2, sharex=True)
+    fig = pickle.loads(pickle.dumps(fig))
+    fig.axes[0].set_xlim(10, 20)
+    assert fig.axes[1].get_xlim() == (10, 20)