matplotlib · lkjell · Dec 4, 2017 · Feb 28, 2018 · Mar 10, 2018 · Mar 14, 2018
diff --git a/doc/api/next_api_changes/2017-12-06-KL.rst b/doc/api/next_api_changes/2017-12-06-KL.rst
@@ -0,0 +1,26 @@
+Change return value of Axes.get_shared_[x,y,z]_axes()
+-----------------------------------------------------
+
+The method `matplotlib.Axes.get_shared_x_axes` (and y and z) used to return `~.cbook.Grouper` objects.
+Now it returns a `~.weakref.WeakSet` object.
+
+Workarounds:
+* If the intention is to get siblings as previous then the WeakSet contains all the siblings.
+An example::
+
+    sharedx = ax.get_shared_x_axes().get_siblings()
+    # is now
+    sharedx = list(ax.get_shared_x_axes())
+
+* If the intention was to use `join` then there is a new share axes method. An example::
+
+    ax1.get_shared_x_axes().join(ax1, ax2)
+    # is now
+    ax1.share_x_axes(ax2)
+
+* If the intention was to check if two elements are in the same group then use the `in` operator. An example::
+
+    ax1.get_shared_x_axes().joined(ax1, ax2)
+    # is now
+    ax2 in ax1.get_shared_x_axes()
+
diff --git a/doc/api/next_api_changes/remove_old_share_axes_after_creation.rst b/doc/api/next_api_changes/remove_old_share_axes_after_creation.rst
@@ -0,0 +1,8 @@
+Remove share through `matplotlib.Axes.get_shared_{x,y,z}_axes`
+--------------------------------------------------------------
+
+Previously when different axes are created with different parent/master axes,
+the share would still be symmetric and transitive if an unconventional
+method through `matplotlib.Axes.get_shared_x_axes`
+is used to share the axes after creation. With the new sharing mechanism
+this is no longer possible.
diff --git a/doc/users/next_whats_new/2017-12-05_share_unshare_axes_after_creation.rst b/doc/users/next_whats_new/2017-12-05_share_unshare_axes_after_creation.rst
@@ -0,0 +1,12 @@
+Share and unshare `axes` after creation
+---------------------------------------
+
+`matplotlib.axes.Axes` have `matplotlib.axes.Axes.unshare_x_axes`,
+`matplotlib.axes.Axes.unshare_y_axes`, `matplotlib.axes.Axes.unshare_z_axes`
+and `matplotlib.axes.Axes.unshare_axes` methods to unshare axes.
+Similiar there are `matplotlib.axes.Axes.share_x_axes`,
+`matplotlib.axes.Axes.share_y_axes`, `matplotlib.axes.Axes.share_z_axes` and
+`matplotlib.axes.Axes.share_axes` methods to share axes.
+
+Unshare an axis will decouple the viewlimits for further changes.
+Share an axis will couple the viewlimits.
diff --git a/examples/mplot3d/share_unshare_3d_axes.py b/examples/mplot3d/share_unshare_3d_axes.py
@@ -0,0 +1,39 @@
+"""
+============================================
+Parametric Curve with Share and Unshare Axes
+============================================
+
+This example demonstrates plotting a parametric curve in 3D,
+and how to share and unshare 3D plot axes.
+"""
+import matplotlib as mpl
+from mpl_toolkits.mplot3d import Axes3D
+import numpy as np
+import matplotlib.pyplot as plt
+
+mpl.rcParams['legend.fontsize'] = 10
+
+# Prepare arrays x, y, z
+theta = np.linspace(-4 * np.pi, 4 * np.pi, 100)
+z = np.linspace(-2, 2, 100)
+r = z ** 2 + 1
+x = r * np.sin(theta)
+y = r * np.cos(theta)
+
+fig = plt.figure()
+ax = fig.add_subplot(311, projection='3d')
+
+ax.plot(x, y, z, label='parametric curve')
+ax.legend()
+
+ax1 = fig.add_subplot(312)
+ax1.plot(range(10))
+ax1.share_axes(ax)
+
+ax2 = fig.add_subplot(313, projection='3d', sharex=ax)
+ax2.plot(x, y, z)
+
+ax2.unshare_x_axes()
+ax2.share_z_axes(ax)
+
+plt.show()
diff --git a/examples/subplots_axes_and_figures/unshare_axis_demo.py b/examples/subplots_axes_and_figures/unshare_axis_demo.py
@@ -0,0 +1,36 @@
+"""
+======================
+Unshare and share axis
+======================
+
+The example shows how to share and unshare axes after they are created.
+"""
+
+import matplotlib.pyplot as plt
+import numpy as np
+
+t = np.arange(0.01, 5.0, 0.01)
+s1 = np.sin(2 * np.pi * t)
+s2 = np.exp(-t)
+s3 = np.sin(4 * np.pi * t)
+
+ax1 = plt.subplot(311)
+plt.plot(t, s1)
+
+ax2 = plt.subplot(312)
+plt.plot(t, s2)
+
+ax3 = plt.subplot(313)
+plt.plot(t, s3)
+
+ax1.share_x_axes(ax2)
+ax1.share_y_axes(ax2)
+
+# Share both axes.
+ax3.share_axes(ax1)
+plt.xlim(0.01, 5.0)
+
+ax3.unshare_y_axes()
+ax2.unshare_x_axes()
+
+plt.show()
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -1,4 +1,6 @@
 from collections import OrderedDict
+from weakref import WeakSet
+import copy
 import itertools
 import logging
 import math
@@ -400,8 +402,6 @@ class _AxesBase(martist.Artist):
     """
     name = "rectilinear"
 
-    _shared_x_axes = cbook.Grouper()
-    _shared_y_axes = cbook.Grouper()
     _twinned_axes = cbook.Grouper()
 
     def __str__(self):
@@ -482,12 +482,18 @@ def __init__(self, fig, rect,
         self._aspect = 'auto'
         self._adjustable = 'box'
         self._anchor = 'C'
+        #Adding yourself to shared xy axes. Reflexive.
+        self._shared_x_axes = WeakSet([self])
+        self._shared_y_axes = WeakSet([self])
         self._sharex = sharex
         self._sharey = sharey
+
         if sharex is not None:
-            self._shared_x_axes.join(self, sharex)
+            self.share_x_axes(sharex)
+
         if sharey is not None:
-            self._shared_y_axes.join(self, sharey)
+            self.share_y_axes(sharey)
+
         self.set_label(label)
         self.set_figure(fig)
 
@@ -571,10 +577,14 @@ def __getstate__(self):
         state.pop('_layoutbox')
         state.pop('_poslayoutbox')
 
+        state['_shared_x_axes'] = list(self._shared_x_axes)
+        state['_shared_y_axes'] = list(self._shared_y_axes)
         return state
 
     def __setstate__(self, state):
         self.__dict__ = state
+        self._shared_x_axes = WeakSet(state['_shared_x_axes'])
+        self._shared_y_axes = WeakSet(state['_shared_y_axes'])
         self._stale = True
         self._layoutbox = None
         self._poslayoutbox = None
@@ -1102,8 +1112,6 @@ def cla(self):
         self.xaxis.set_clip_path(self.patch)
         self.yaxis.set_clip_path(self.patch)
 
-        self._shared_x_axes.clean()
-        self._shared_y_axes.clean()
         if self._sharex:
             self.xaxis.set_visible(xaxis_visible)
             self.patch.set_visible(patch_visible)
@@ -1280,8 +1288,7 @@ def set_aspect(self, aspect, adjustable=None, anchor=None, share=False):
         if not (isinstance(aspect, str) and aspect in ('equal', 'auto')):
             aspect = float(aspect)  # raise ValueError if necessary
         if share:
-            axes = set(self._shared_x_axes.get_siblings(self)
-                       + self._shared_y_axes.get_siblings(self))
+            axes = set(self._shared_x_axes | self._shared_y_axes)
         else:
             axes = [self]
         for ax in axes:
@@ -1335,8 +1342,7 @@ def set_adjustable(self, adjustable, share=False):
         if adjustable not in ('box', 'datalim', 'box-forced'):
             raise ValueError("argument must be 'box', or 'datalim'")
         if share:
-            axes = set(self._shared_x_axes.get_siblings(self)
-                       + self._shared_y_axes.get_siblings(self))
+            axes = set(self._shared_x_axes | self._shared_y_axes)
         else:
             axes = [self]
         for ax in axes:
@@ -1403,8 +1409,7 @@ def set_anchor(self, anchor, share=False):
             raise ValueError('argument must be among %s' %
                              ', '.join(mtransforms.Bbox.coefs))
         if share:
-            axes = set(self._shared_x_axes.get_siblings(self)
-                       + self._shared_y_axes.get_siblings(self))
+            axes = set(self._shared_x_axes | self._shared_y_axes)
         else:
             axes = [self]
         for ax in axes:
@@ -1556,8 +1561,8 @@ def apply_aspect(self, position=None):
         xm = 0
         ym = 0
 
-        shared_x = self in self._shared_x_axes
-        shared_y = self in self._shared_y_axes
+        shared_x = self.is_sharing_x_axes()
+        shared_y = self.is_sharing_y_axes()
         # Not sure whether we need this check:
         if shared_x and shared_y:
             raise RuntimeError("adjustable='datalim' is not allowed when both"
@@ -2389,8 +2394,7 @@ def handle_single_axis(scale, autoscaleon, shared_axes, interval,
             if not (scale and autoscaleon):
                 return  # nothing to do...
 
-            shared = shared_axes.get_siblings(self)
-            dl = [ax.dataLim for ax in shared]
+            dl = [ax.dataLim for ax in shared_axes]
             # ignore non-finite data limits if good limits exist
             finite_dl = [d for d in dl if np.isfinite(d).all()]
             if len(finite_dl):
@@ -3126,7 +3130,7 @@ def set_xlim(self, left=None, right=None, emit=True, auto=False,
         if emit:
             self.callbacks.process('xlim_changed', self)
             # Call all of the other x-axes that are shared with this one
-            for other in self._shared_x_axes.get_siblings(self):
+            for other in self._shared_x_axes:
                 if other is not self:
                     other.set_xlim(self.viewLim.intervalx,
                                    emit=False, auto=auto)
@@ -3165,8 +3169,7 @@ def set_xscale(self, value, **kwargs):
 
         matplotlib.scale.LogisticTransform : logit transform
         """
-        g = self.get_shared_x_axes()
-        for ax in g.get_siblings(self):
+        for ax in self._shared_x_axes:
             ax.xaxis._set_scale(value, **kwargs)
             ax._update_transScale()
             ax.stale = True
@@ -3459,7 +3462,7 @@ def set_ylim(self, bottom=None, top=None, emit=True, auto=False,
         if emit:
             self.callbacks.process('ylim_changed', self)
             # Call all of the other y-axes that are shared with this one
-            for other in self._shared_y_axes.get_siblings(self):
+            for other in self._shared_y_axes:
                 if other is not self:
                     other.set_ylim(self.viewLim.intervaly,
                                    emit=False, auto=auto)
@@ -3498,8 +3501,7 @@ def set_yscale(self, value, **kwargs):
 
         matplotlib.scale.LogisticTransform : logit transform
         """
-        g = self.get_shared_y_axes()
-        for ax in g.get_siblings(self):
+        for ax in self._shared_y_axes:
             ax.yaxis._set_scale(value, **kwargs)
             ax._update_transScale()
             ax.stale = True
@@ -4231,9 +4233,100 @@ def twiny(self):
         return ax2
 
     def get_shared_x_axes(self):
-        """Return a reference to the shared axes Grouper object for x axes."""
-        return self._shared_x_axes
+        """Return a copy of the shared axes Weakset object for x axes"""
+        return WeakSet(self._shared_x_axes)
 
     def get_shared_y_axes(self):
-        """Return a reference to the shared axes Grouper object for y axes."""
-        return self._shared_y_axes
+        """Return a copy of the shared axes Weakset object for y axes"""
+        return WeakSet(self._shared_y_axes)
+
+    def is_sharing_x_axes(self):
+        return len(self.get_shared_x_axes()) > 1
+
+    def is_sharing_y_axes(self):
+        return len(self.get_shared_y_axes()) > 1
+
+    def _unshare_axes(self, shared_axes):
+        for ax in getattr(self, "_shared_{}_axes".format(shared_axes)):
+            parent = getattr(ax, "_share{}".format(shared_axes))
+
+            if parent is self:
+                setattr(ax, "_share{}".format(shared_axes), None)
+                self._copy_axis_major_minor(
+                    getattr(ax, "{}axis".format(shared_axes)))
+
+        getattr(self, "_shared_{}_axes".format(shared_axes)).remove(self)
+        setattr(self, "_shared_{}_axes".format(shared_axes), WeakSet([self]))
+        setattr(self, "_share{}".format(shared_axes), None)
+
+        self._copy_axis_major_minor(
+            getattr(self, "{}axis".format(shared_axes)))
+
+    @staticmethod
+    def _copy_axis_major_minor(axis):
+        major = axis.major
+        minor = axis.minor
+
+        axis.major = copy.deepcopy(major)
+        axis.minor = copy.deepcopy(minor)
+
+        axis.major.set_axis(axis)
+        axis.minor.set_axis(axis)
+
+    def unshare_x_axes(self):
+        """ Unshare x axis. """
+        self._unshare_axes("x")
+
+    def unshare_y_axes(self):
+        """ Unshare y axis. """
+        self._unshare_axes("y")
+
+    def unshare_axes(self):
+        """ Unshare both x and y axes. """
+        self.unshare_x_axes()
+        self.unshare_y_axes()
+
+    def _share_axes(self, axes, shared_axes):
+        if not iterable(axes):
+            axes = [axes]
+
+        shared = getattr(self, "_shared_{}_axes".format(shared_axes))
+        for ax in axes:
+            shared |= getattr(ax, "_shared_{}_axes".format(shared_axes))
+
+        for ax in shared:
+            setattr(ax, "_shared_{}_axes".format(shared_axes), shared)
+
+    def share_x_axes(self, axes):
+        """
+        Share x axis.
+
+        Parameters
+        ----------
+        axes: Axes
+            Axes to share.
+        """
+        self._share_axes(axes, 'x')
+
+    def share_y_axes(self, axes):
+        """
+        Share y axis.
+
+        Parameters
+        ----------
+        axes: Axes
+            Axes to share.
+        """
+        self._share_axes(axes, 'y')
+
+    def share_axes(self, axes):
+        """
+        Share both x and y axes.
+
+        Parameters
+        ----------
+        axes: Axes
+            Axes to share.
+        """
+        self.share_x_axes(axes)
+        self.share_y_axes(axes)