matplotlib · tacaswell · Oct 20, 2022 · Aug 6, 2022 · QuLogic · Oct 21, 2022
diff --git a/doc/api/axes_api.rst b/doc/api/axes_api.rst
@@ -27,18 +27,6 @@ The Axes class
    :no-undoc-members:
    :show-inheritance:
 
-
-Subplots
-========
-
-.. autosummary::
-   :toctree: _as_gen
-   :template: autosummary.rst
-   :nosignatures:
-
-   SubplotBase
-   subplot_class_factory
-
 Plotting
 ========
 
@@ -313,6 +301,7 @@ Axis labels, title, and legend
    Axes.get_xlabel
    Axes.set_ylabel
    Axes.get_ylabel
+   Axes.label_outer
 
    Axes.set_title
    Axes.get_title
@@ -484,6 +473,9 @@ Axes position
    Axes.get_axes_locator
    Axes.set_axes_locator
 
+   Axes.get_subplotspec
+   Axes.set_subplotspec
+
    Axes.reset_position
 
    Axes.get_position

diff --git a/doc/api/next_api_changes/behavior/23573-AL.rst b/doc/api/next_api_changes/behavior/23573-AL.rst
@@ -0,0 +1,7 @@
+All Axes have ``get_subplotspec`` and ``get_gridspec`` methods now, which returns None for Axes not positioned via a gridspec
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Previously, this method was only present for Axes positioned via a gridspec.
+Following this change, checking ``hasattr(ax, "get_gridspec")`` should now be
+replaced by ``ax.get_gridspec() is not None``.  For compatibility with older
+Matplotlib releases, one can also check
+``hasattr(ax, "get_gridspec") and ax.get_gridspec() is not None``.
diff --git a/doc/api/prev_api_changes/api_changes_3.3.0/deprecations.rst b/doc/api/prev_api_changes/api_changes_3.3.0/deprecations.rst
@@ -328,7 +328,7 @@ are deprecated.  Panning and zooming are now implemented using the
 
 Passing None to various Axes subclass factories
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-Support for passing ``None`` as base class to `.axes.subplot_class_factory`,
+Support for passing ``None`` as base class to ``axes.subplot_class_factory``,
 ``axes_grid1.parasite_axes.host_axes_class_factory``,
 ``axes_grid1.parasite_axes.host_subplot_class_factory``,
 ``axes_grid1.parasite_axes.parasite_axes_class_factory``, and

diff --git a/doc/api/prev_api_changes/api_changes_3.4.0/deprecations.rst b/doc/api/prev_api_changes/api_changes_3.4.0/deprecations.rst
@@ -38,8 +38,8 @@ Subplot-related attributes and methods
 Some ``SubplotBase`` methods and attributes have been deprecated and/or moved
 to `.SubplotSpec`:
 
-- ``get_geometry`` (use `.SubplotBase.get_subplotspec` instead),
-- ``change_geometry`` (use `.SubplotBase.set_subplotspec` instead),
+- ``get_geometry`` (use ``SubplotBase.get_subplotspec`` instead),
+- ``change_geometry`` (use ``SubplotBase.set_subplotspec`` instead),
 - ``is_first_row``, ``is_last_row``, ``is_first_col``, ``is_last_col`` (use the
   corresponding methods on the `.SubplotSpec` instance instead),
 - ``update_params`` (now a no-op),

diff --git a/doc/users/prev_whats_new/whats_new_3.0.rst b/doc/users/prev_whats_new/whats_new_3.0.rst
@@ -141,10 +141,10 @@ independent on the axes size or units. To revert to the previous behaviour
 set the axes' aspect ratio to automatic by using ``ax.set_aspect("auto")`` or
 ``plt.axis("auto")``.
 
-Add ``ax.get_gridspec`` to `.SubplotBase`
------------------------------------------
+Add ``ax.get_gridspec`` to ``SubplotBase``
+------------------------------------------
 
-New method `.SubplotBase.get_gridspec` is added so that users can
+New method ``SubplotBase.get_gridspec`` is added so that users can
 easily get the gridspec that went into making an axes:
 
   .. code::

diff --git a/lib/matplotlib/_constrained_layout.py b/lib/matplotlib/_constrained_layout.py
@@ -187,8 +187,8 @@ def make_layoutgrids(fig, layoutgrids, rect=(0, 0, 1, 1)):
 
     # for each axes at the local level add its gridspec:
     for ax in fig._localaxes:
-        if hasattr(ax, 'get_subplotspec'):
-            gs = ax.get_subplotspec().get_gridspec()
+        gs = ax.get_gridspec()
+        if gs is not None:
             layoutgrids = make_layoutgrids_gs(layoutgrids, gs)
 
     return layoutgrids
@@ -248,24 +248,22 @@ def check_no_collapsed_axes(layoutgrids, fig):
         ok = check_no_collapsed_axes(layoutgrids, sfig)
         if not ok:
             return False
-
     for ax in fig.axes:
-        if hasattr(ax, 'get_subplotspec'):
-            gs = ax.get_subplotspec().get_gridspec()
-            if gs in layoutgrids:
-                lg = layoutgrids[gs]
-                for i in range(gs.nrows):
-                    for j in range(gs.ncols):
-                        bb = lg.get_inner_bbox(i, j)
-                        if bb.width <= 0 or bb.height <= 0:
-                            return False
+        gs = ax.get_gridspec()
+        if gs in layoutgrids:  # also implies gs is not None.
+            lg = layoutgrids[gs]
+            for i in range(gs.nrows):
+                for j in range(gs.ncols):
+                    bb = lg.get_inner_bbox(i, j)
+                    if bb.width <= 0 or bb.height <= 0:
+                        return False
     return True
 
 
 def compress_fixed_aspect(layoutgrids, fig):
     gs = None
     for ax in fig.axes:
-        if not hasattr(ax, 'get_subplotspec'):
+        if ax.get_subplotspec() is None:
             continue
         ax.apply_aspect()
         sub = ax.get_subplotspec()
@@ -357,7 +355,7 @@ def make_layout_margins(layoutgrids, fig, renderer, *, w_pad=0, h_pad=0,
         layoutgrids[sfig].parent.edit_outer_margin_mins(margins, ss)
 
     for ax in fig._localaxes:
-        if not hasattr(ax, 'get_subplotspec') or not ax.get_in_layout():
+        if not ax.get_subplotspec() or not ax.get_in_layout():
             continue
 
         ss = ax.get_subplotspec()
@@ -488,8 +486,8 @@ def match_submerged_margins(layoutgrids, fig):
     for sfig in fig.subfigs:
         match_submerged_margins(layoutgrids, sfig)
 
-    axs = [a for a in fig.get_axes() if (hasattr(a, 'get_subplotspec')
-                                         and a.get_in_layout())]
+    axs = [a for a in fig.get_axes()
+           if a.get_subplotspec() is not None and a.get_in_layout()]
 
     for ax1 in axs:
         ss1 = ax1.get_subplotspec()
@@ -620,7 +618,7 @@ def reposition_axes(layoutgrids, fig, renderer, *,
                         wspace=wspace, hspace=hspace)
 
     for ax in fig._localaxes:
-        if not hasattr(ax, 'get_subplotspec') or not ax.get_in_layout():
+        if ax.get_subplotspec() is None or not ax.get_in_layout():
             continue
 
         # grid bbox is in Figure coordinates, but we specify in panel
@@ -742,10 +740,9 @@ def reset_margins(layoutgrids, fig):
     for sfig in fig.subfigs:
         reset_margins(layoutgrids, sfig)
     for ax in fig.axes:
-        if hasattr(ax, 'get_subplotspec') and ax.get_in_layout():
-            ss = ax.get_subplotspec()
-            gs = ss.get_gridspec()
-            if gs in layoutgrids:
+        if ax.get_in_layout():
+            gs = ax.get_gridspec()
+            if gs in layoutgrids:  # also implies gs is not None.
                 layoutgrids[gs].reset_margins()
     layoutgrids[fig].reset_margins()
 

diff --git a/lib/matplotlib/axes/__init__.py b/lib/matplotlib/axes/__init__.py
@@ -1,2 +1,18 @@
-from ._subplots import *
+from . import _base
 from ._axes import *
+
+# Backcompat.
+from ._axes import Axes as Subplot
+
+
+class _SubplotBaseMeta(type):
+    def __instancecheck__(self, obj):
+        return (isinstance(obj, _base._AxesBase)
+                and obj.get_subplotspec() is not None)
+
+
+class SubplotBase(metaclass=_SubplotBaseMeta):
+    pass
+
+
+def subplot_class_factory(cls): return cls
diff --git a/lib/matplotlib/axes/_base.py b/lib/matplotlib/axes/_base.py
@@ -1,4 +1,4 @@
-from collections.abc import MutableSequence
+from collections.abc import Iterable, MutableSequence
 from contextlib import ExitStack
 import functools
 import inspect
@@ -18,6 +18,7 @@
 import matplotlib.collections as mcoll
 import matplotlib.colors as mcolors
 import matplotlib.font_manager as font_manager
+from matplotlib.gridspec import SubplotSpec
 import matplotlib.image as mimage
 import matplotlib.lines as mlines
 import matplotlib.patches as mpatches
@@ -569,8 +570,8 @@ 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)
 
-    def __init__(self, fig, rect,
-                 *,
+    def __init__(self, fig,
+                 *args,
                  facecolor=None,  # defaults to rc axes.facecolor
                  frameon=True,
                  sharex=None,  # use Axes instance's xaxis info
@@ -589,9 +590,18 @@ def __init__(self, fig, rect,
         fig : `~matplotlib.figure.Figure`
             The Axes is built in the `.Figure` *fig*.
 
-        rect : tuple (left, bottom, width, height).
-            The Axes is built in the rectangle *rect*. *rect* is in
-            `.Figure` coordinates.
+        *args
+            ``*args`` can be a single ``(left, bottom, width, height)``
+            rectangle or a single `.Bbox`.  This specifies the rectangle (in
+            figure coordinates) where the Axes is positioned.
+
+            ``*args`` can also consist of three numbers or a single three-digit
+            number; in the latter case, the digits are considered as
+            independent numbers.  The numbers are interpreted as ``(nrows,
+            ncols, index)``: ``(nrows, ncols)`` specifies the size of an array
+            of subplots, and ``index`` is the 1-based index of the subplot
+            being created.  Finally, ``*args`` can also directly be a
+            `.SubplotSpec` instance.
 
         sharex, sharey : `~.axes.Axes`, optional
             The x or y `~.matplotlib.axis` is shared with the x or
@@ -616,10 +626,21 @@ def __init__(self, fig, rect,
         """
 
         super().__init__()
-        if isinstance(rect, mtransforms.Bbox):
-            self._position = rect
+        if "rect" in kwargs:
+            if args:
+                raise TypeError(
+                    "'rect' cannot be used together with positional arguments")
+            rect = kwargs.pop("rect")
+            _api.check_isinstance((mtransforms.Bbox, Iterable), rect=rect)
+            args = (rect,)
+        subplotspec = None
+        if len(args) == 1 and isinstance(args[0], mtransforms.Bbox):
+            self._position = args[0]
+        elif len(args) == 1 and np.iterable(args[0]):
+            self._position = mtransforms.Bbox.from_bounds(*args[0])
         else:
-            self._position = mtransforms.Bbox.from_bounds(*rect)
+            self._position = self._originalPosition = mtransforms.Bbox.unit()
+            subplotspec = SubplotSpec._from_subplot_args(fig, args)
         if self._position.width < 0 or self._position.height < 0:
             raise ValueError('Width and height specified must be non-negative')
         self._originalPosition = self._position.frozen()
@@ -632,8 +653,16 @@ def __init__(self, fig, rect,
         self._sharey = sharey
         self.set_label(label)
         self.set_figure(fig)
+        # The subplotspec needs to be set after the figure (so that
+        # figure-level subplotpars are taken into account), but the figure
+        # needs to be set after self._position is initialized.
+        if subplotspec:
+            self.set_subplotspec(subplotspec)
+        else:
+            self._subplotspec = None
         self.set_box_aspect(box_aspect)
         self._axes_locator = None  # Optionally set via update(kwargs).
+
         # placeholder for any colorbars added that use this Axes.
         # (see colorbar.py):
         self._colorbars = []
@@ -737,6 +766,19 @@ def __repr__(self):
                 fields += [f"{name}label={axis.get_label().get_text()!r}"]
         return f"<{self.__class__.__name__}: " + ", ".join(fields) + ">"
 
+    def get_subplotspec(self):
+        """Return the `.SubplotSpec` associated with the subplot, or None."""
+        return self._subplotspec
+
+    def set_subplotspec(self, subplotspec):
+        """Set the `.SubplotSpec`. associated with the subplot."""
+        self._subplotspec = subplotspec
+        self._set_position(subplotspec.get_position(self.figure))
+
+    def get_gridspec(self):
+        """Return the `.GridSpec` associated with the subplot, or None."""
+        return self._subplotspec.get_gridspec() if self._subplotspec else None
+
     @_api.delete_parameter("3.6", "args")
     @_api.delete_parameter("3.6", "kwargs")
     def get_window_extent(self, renderer=None, *args, **kwargs):
@@ -4424,17 +4466,23 @@ def get_tightbbox(self, renderer=None, call_axes_locator=True,
 
     def _make_twin_axes(self, *args, **kwargs):
         """Make a twinx Axes of self. This is used for twinx and twiny."""
-        # Typically, SubplotBase._make_twin_axes is called instead of this.
         if 'sharex' in kwargs and 'sharey' in kwargs:
-            raise ValueError("Twinned Axes may share only one axis")
-        ax2 = self.figure.add_axes(
-            self.get_position(True), *args, **kwargs,
-            axes_locator=_TransformedBoundsLocator(
-                [0, 0, 1, 1], self.transAxes))
+            # The following line is added in v2.2 to avoid breaking Seaborn,
+            # which currently uses this internal API.
+            if kwargs["sharex"] is not self and kwargs["sharey"] is not self:
+                raise ValueError("Twinned Axes may share only one axis")
+        ss = self.get_subplotspec()
+        if ss:
+            twin = self.figure.add_subplot(ss, *args, **kwargs)
+        else:
+            twin = self.figure.add_axes(
+                self.get_position(True), *args, **kwargs,
+                axes_locator=_TransformedBoundsLocator(
+                    [0, 0, 1, 1], self.transAxes))
         self.set_adjustable('datalim')
-        ax2.set_adjustable('datalim')
-        self._twinned_axes.join(self, ax2)
-        return ax2
+        twin.set_adjustable('datalim')
+        self._twinned_axes.join(self, twin)
+        return twin
 
     def twinx(self):
         """
@@ -4502,3 +4550,56 @@ def get_shared_x_axes(self):
     def get_shared_y_axes(self):
         """Return an immutable view on the shared y-axes Grouper."""
         return cbook.GrouperView(self._shared_axes["y"])
+
+    def label_outer(self):
+        """
+        Only show "outer" labels and tick labels.
+
+        x-labels are only kept for subplots on the last row (or first row, if
+        labels are on the top side); y-labels only for subplots on the first
+        column (or last column, if labels are on the right side).
+        """
+        self._label_outer_xaxis(check_patch=False)
+        self._label_outer_yaxis(check_patch=False)
+
+    def _label_outer_xaxis(self, *, check_patch):
+        # see documentation in label_outer.
+        if check_patch and not isinstance(self.patch, mpl.patches.Rectangle):
+            return
+        ss = self.get_subplotspec()
+        if not ss:
+            return
+        label_position = self.xaxis.get_label_position()
+        if not ss.is_first_row():  # Remove top label/ticklabels/offsettext.
+            if label_position == "top":
+                self.set_xlabel("")
+            self.xaxis.set_tick_params(which="both", labeltop=False)
+            if self.xaxis.offsetText.get_position()[1] == 1:
+                self.xaxis.offsetText.set_visible(False)
+        if not ss.is_last_row():  # Remove bottom label/ticklabels/offsettext.
+            if label_position == "bottom":
+                self.set_xlabel("")
+            self.xaxis.set_tick_params(which="both", labelbottom=False)
+            if self.xaxis.offsetText.get_position()[1] == 0:
+                self.xaxis.offsetText.set_visible(False)
+
+    def _label_outer_yaxis(self, *, check_patch):
+        # see documentation in label_outer.
+        if check_patch and not isinstance(self.patch, mpl.patches.Rectangle):
+            return
+        ss = self.get_subplotspec()
+        if not ss:
+            return
+        label_position = self.yaxis.get_label_position()
+        if not ss.is_first_col():  # Remove left label/ticklabels/offsettext.
+            if label_position == "left":
+                self.set_ylabel("")
+            self.yaxis.set_tick_params(which="both", labelleft=False)
+            if self.yaxis.offsetText.get_position()[0] == 0:
+                self.yaxis.offsetText.set_visible(False)
+        if not ss.is_last_col():  # Remove right label/ticklabels/offsettext.
+            if label_position == "right":
+                self.set_ylabel("")
+            self.yaxis.set_tick_params(which="both", labelright=False)
+            if self.yaxis.offsetText.get_position()[0] == 1:
+                self.yaxis.offsetText.set_visible(False)