MNT: Improve Grouper

- add Grouper.get_siblings(..., include_self=...) parameter
- `Axes._shared_axes` is a class variable. Therefore, we can make `get_shared_x/y_axes()` class methods.

This is in preparations of matplotlib#30159 (comment).

Author: timhoffm

lib/matplotlib/axes/_base.py

@@ -4756,13 +4756,15 @@ def twiny(self, axes_class=None, **kwargs):
         ax2.yaxis.units = self.yaxis.units
         return ax2
 
-    def get_shared_x_axes(self):
+    @classmethod
+    def get_shared_x_axes(cls):
         """Return an immutable view on the shared x-axes Grouper."""
-        return cbook.GrouperView(self._shared_axes["x"])
+        return cbook.GrouperView(cls._shared_axes["x"])
 
-    def get_shared_y_axes(self):
+    @classmethod
+    def get_shared_y_axes(cls):
         """Return an immutable view on the shared y-axes Grouper."""
-        return cbook.GrouperView(self._shared_axes["y"])
+        return cbook.GrouperView(cls._shared_axes["y"])
 
     def label_outer(self, remove_inner_ticks=False):
         """

lib/matplotlib/axes/_base.pyi

@@ -388,8 +388,10 @@ class _AxesBase(martist.Artist):
     ) -> Bbox | None: ...
     def twinx(self, axes_class: Axes | None = ..., **kwargs) -> Axes: ...
     def twiny(self, axes_class: Axes | None = ..., **kwargs) -> Axes: ...
-    def get_shared_x_axes(self) -> cbook.GrouperView: ...
-    def get_shared_y_axes(self) -> cbook.GrouperView: ...
+    @classmethod
+    def get_shared_x_axes(cls) -> cbook.GrouperView: ...
+    @classmethod
+    def get_shared_y_axes(cls) -> cbook.GrouperView: ...
     def label_outer(self, remove_inner_ticks: bool = ...) -> None: ...
 
     # The methods underneath this line are added via the `_axis_method_wrapper` class

lib/matplotlib/axis.py

@@ -703,7 +703,7 @@ def isDefault_minfmt(self, value):
         self.minor._formatter_is_default = value
 
     def _get_shared_axes(self):
-        """Return Grouper of shared Axes for current axis."""
+        """Return a list of shared Axes for current axis."""
         return self.axes._shared_axes[
             self._get_axis_name()].get_siblings(self.axes)
 

lib/matplotlib/cbook.py

@@ -886,10 +886,17 @@ def __iter__(self):
         for group in unique_groups.values():
             yield sorted(group, key=self._ordering.__getitem__)
 
-    def get_siblings(self, a):
-        """Return all of the items joined with *a*, including itself."""
+    def get_siblings(self, a, *, include_self=True):
+        """
+        Return all the items joined with *a*.
+
+        *a* is included in the list if *include_self* is True.
+        """
         siblings = self._mapping.get(a, [a])
-        return sorted(siblings, key=self._ordering.get)
+        result = sorted(siblings, key=self._ordering.get)
+        if not include_self:
+            result.remove(a)
+        return result
 
 
 class GrouperView:
@@ -905,11 +912,13 @@ def joined(self, a, b):
         """
         return self._grouper.joined(a, b)
 
-    def get_siblings(self, a):
+    def get_siblings(self, a, *, include_self=True):
         """
-        Return all of the items joined with *a*, including itself.
+        Return all the items joined with *a*.
+
+        *a* is included in the list if *include_self* is True.
         """
-        return self._grouper.get_siblings(a)
+        return self._grouper.get_siblings(a, include_self=include_self)
 
 
 def simple_linear_interpolation(a, steps):

lib/matplotlib/cbook.pyi

@@ -107,14 +107,14 @@ class Grouper(Generic[_T]):
     def joined(self, a: _T, b: _T) -> bool: ...
     def remove(self, a: _T) -> None: ...
     def __iter__(self) -> Iterator[list[_T]]: ...
-    def get_siblings(self, a: _T) -> list[_T]: ...
+    def get_siblings(self, a: _T, *, include_self: bool = True) -> list[_T]: ...
 
 class GrouperView(Generic[_T]):
     def __init__(self, grouper: Grouper[_T]) -> None: ...
     def __contains__(self, item: _T) -> bool: ...
     def __iter__(self) -> Iterator[list[_T]]: ...
     def joined(self, a: _T, b: _T) -> bool: ...
-    def get_siblings(self, a: _T) -> list[_T]: ...
+    def get_siblings(self, a: _T, *, include_self: bool = True) -> list[_T]: ...
 
 def simple_linear_interpolation(a: ArrayLike, steps: int) -> np.ndarray: ...
 def delete_masked_points(*args): ...

lib/matplotlib/figure.py

@@ -947,7 +947,7 @@ def _remove_axes(self, ax, owners):
 
         for name in ax._axis_names:  # Break link between any shared Axes
             grouper = ax._shared_axes[name]
-            siblings = [other for other in grouper.get_siblings(ax) if other is not ax]
+            siblings = grouper.get_siblings(ax, include_self=False)
             if not siblings:  # Axes was not shared along this axis; we're done.
                 continue
             grouper.remove(ax)

lib/matplotlib/tests/test_cbook.py

@@ -622,6 +622,7 @@ class Dummy:
     g.join(*objs)
     assert set(list(g)[0]) == set(objs)
     assert set(g.get_siblings(a)) == set(objs)
+    assert a not in g.get_siblings(a, include_self=False)
 
     for other in objs[1:]:
         assert g.joined(a, other)