DOC: remove some usages of None as explicit defaults

In docs, we rather specify "optional" instead of "default: None" when
None is only used as a sentinel for "not given". We also specify
prefer concrete types or rc references over None usage if possible.

Author: timhoffm

lib/mpl_toolkits/axes_grid1/axes_grid.py

@@ -84,8 +84,8 @@ def __init__(self, fig,
             ``121``), or as a `~.SubplotSpec`.
         nrows_ncols : (int, int)
             Number of rows and columns in the grid.
-        n_axes : int or None, default: None
-            If not None, only the first *n_axes* axes in the grid are created.
+        n_axes : int, optional
+            If given, only the first *n_axes* axes in the grid are created.
         direction : {"row", "column"}, default: "row"
             Whether axes are created in row-major ("row by row") or
             column-major order ("column by column").  This also affects the
@@ -109,7 +109,7 @@ def __init__(self, fig,
             - "all": All axes are labelled.
             - "keep": Do not do anything.
 
-        axes_class : subclass of `matplotlib.axes.Axes`, default: `.mpl_axes.Axes`
+        axes_class : subclass of `matplotlib.axes.Axes`, default: `~.mpl_axes.Axes`
             The type of Axes to create.
         aspect : bool, default: False
             Whether the axes aspect ratio follows the aspect ratio of the data
@@ -322,8 +322,8 @@ def __init__(self, fig,
             as a three-digit subplot position code (e.g., "121").
         nrows_ncols : (int, int)
             Number of rows and columns in the grid.
-        n_axes : int or None, default: None
-            If not None, only the first *n_axes* axes in the grid are created.
+        n_axes : int, optional
+            If given, only the first *n_axes* axes in the grid are created.
         direction : {"row", "column"}, default: "row"
             Whether axes are created in row-major ("row by row") or
             column-major order ("column by column").  This also affects the
@@ -364,7 +364,7 @@ def __init__(self, fig,
         cbar_set_cax : bool, default: True
             If True, each axes in the grid has a *cax* attribute that is bound
             to associated *cbar_axes*.
-        axes_class : subclass of `matplotlib.axes.Axes`, default: None
+        axes_class : subclass of `matplotlib.axes.Axes`, default: `~.mpl_axes.Axes`
         """
         _api.check_in_list(["each", "single", "edge", None],
                            cbar_mode=cbar_mode)

lib/mpl_toolkits/mplot3d/art3d.py

@@ -737,9 +737,8 @@ def set_depthshade(
         depthshade : bool
             Whether to shade the patches in order to give the appearance of
             depth.
-        depthshade_minalpha : float, default: None
+        depthshade_minalpha : float, default: :rc:`axes3d.depthshade_minalpha`
             Sets the minimum alpha value used by depth-shading.
-            If None, use the value from rcParams['axes3d.depthshade_minalpha'].
 
             .. versionadded:: 3.11
         """
@@ -1112,17 +1111,15 @@ def patch_collection_2d_to_3d(
     zdir : {'x', 'y', 'z'}
         The axis in which to place the patches. Default: "z".
         See `.get_dir_vector` for a description of the values.
-    depthshade : bool, default: None
+    depthshade : bool, default: :rc:`axes3d.depthshade`
         Whether to shade the patches to give a sense of depth.
-        If None, use the value from rcParams['axes3d.depthshade'].
     axlim_clip : bool, default: False
         Whether to hide patches with a vertex outside the axes view limits.
 
         .. versionadded:: 3.10
 
-    depthshade_minalpha : float, default: None
+    depthshade_minalpha : float, default: :rc:`axes3d.depthshade_minalpha`
         Sets the minimum alpha value used by depth-shading.
-        If None, use the value from rcParams['axes3d.depthshade_minalpha'].
 
         .. versionadded:: 3.11
     """

lib/mpl_toolkits/mplot3d/axes3d.py

@@ -58,7 +58,7 @@ class Axes3D(Axes):
     Axes._shared_axes["view"] = cbook.Grouper()
 
     def __init__(
-        self, fig, rect=None, *args,
+        self, fig, rect=(0, 0, 1, 1), *args,
         elev=30, azim=-60, roll=0, shareview=None, sharez=None,
         proj_type='persp', focal_length=None,
         box_aspect=None,
@@ -70,7 +70,7 @@ def __init__(
         ----------
         fig : Figure
             The parent figure.
-        rect : tuple (left, bottom, width, height), default: None.
+        rect : tuple (left, bottom, width, height), default: (0, 0, 1, 1)
             The ``(left, bottom, width, height)`` Axes position.
         elev : float, default: 30
             The elevation angle in degrees rotates the camera above and below
@@ -119,10 +119,6 @@ def __init__(
 
             %(Axes3D:kwdoc)s
         """
-
-        if rect is None:
-            rect = [0.0, 0.0, 1.0, 1.0]
-
         self.initial_azim = azim
         self.initial_elev = elev
         self.initial_roll = roll
@@ -2049,9 +2045,10 @@ def fill_between(self, x1, y1, z1, x2, y2, z2, *,
             - 'auto': If the points all lie on the same 3D plane, 'polygon' is
               used. Otherwise, 'quad' is used.
 
-        facecolors : list of :mpltype:`color`, default: None
+        facecolors : :mpltype:`color` or list of :mpltype:`color`, optional
             Colors of each individual patch, or a single color to be used for
-            all patches.
+            all patches. If not given, the next color from the patch color
+            cycle is used.
 
         shade : bool, default: None
             Whether to shade the facecolors. If *None*, then defaults to *True*
@@ -2943,15 +2940,13 @@ def scatter(self, xs, ys, zs=0, zdir='z', s=20, c=None, depthshade=None,
             - A 2D array in which the rows are RGB or RGBA.
 
             For more details see the *c* argument of `~.axes.Axes.scatter`.
-        depthshade : bool, default: None
+        depthshade : bool, default: :rc:`axes3d.depthshade`
             Whether to shade the scatter markers to give the appearance of
             depth. Each call to ``scatter()`` will perform its depthshading
             independently.
-            If None, use the value from rcParams['axes3d.depthshade'].
 
-        depthshade_minalpha : float, default: None
+        depthshade_minalpha : float, default: :rc:`axes3d.depthshade_minalpha`
             The lowest alpha value applied by depth-shading.
-            If None, use the value from rcParams['axes3d.depthshade_minalpha'].
 
             .. versionadded:: 3.11
 
@@ -3627,12 +3622,12 @@ def errorbar(self, x, y, z, zerr=None, yerr=None, xerr=None, fmt='',
             Use 'none' (case-insensitive) to plot errorbars without any data
             markers.
 
-        ecolor : :mpltype:`color`, default: None
-            The color of the errorbar lines.  If None, use the color of the
+        ecolor : :mpltype:`color`, optional
+            The color of the errorbar lines. If not given, use the color of the
             line connecting the markers.
 
-        elinewidth : float, default: None
-            The linewidth of the errorbar lines. If None, the linewidth of
+        elinewidth : float, optional
+            The linewidth of the errorbar lines. If not given, the linewidth of
             the current style is used.
 
         capsize : float, default: :rc:`errorbar.capsize`