Make .axis(zmin=...) work on 3D axes

This adds an `_axis_names` member to make it possible to generalize parts of `_AxesBase` to work in 3D too.

Author: eric-wieser

lib/matplotlib/axes/_base.py

@@ -2099,28 +2099,34 @@ def axis(self, arg=None, /, *, emit=True, **kwargs):
                                  "try 'on' or 'off'")
         else:
             if arg is not None:
-                try:
-                    xmin, xmax, ymin, ymax = arg
-                except (TypeError, ValueError) as err:
-                    raise TypeError('the first argument to axis() must be an '
-                                    'iterable of the form '
-                                    '[xmin, xmax, ymin, ymax]') from err
+                if len(arg) != 2*len(self._axis_names):
+                    raise TypeError(
+                        "The first argument to axis() must be an iterable of the form "
+                        "[{}]".format(", ".join(
+                            f"{name}min, {name}max" for name in self._axis_names)))
+                limits = {
+                    name: arg[2*i:2*(i+1)]
+                    for i, name in enumerate(self._axis_names)
+                }
             else:
-                xmin = kwargs.pop('xmin', None)
-                xmax = kwargs.pop('xmax', None)
-                ymin = kwargs.pop('ymin', None)
-                ymax = kwargs.pop('ymax', None)
-            xauto = (None  # Keep autoscale state as is.
-                     if xmin is None and xmax is None
-                     else False)  # Turn off autoscale.
-            yauto = (None
-                     if ymin is None and ymax is None
-                     else False)
-            self.set_xlim(xmin, xmax, emit=emit, auto=xauto)
-            self.set_ylim(ymin, ymax, emit=emit, auto=yauto)
+                limits = {}
+                for name in self._axis_names:
+                    ax_min = kwargs.pop(f'{name}min', None)
+                    ax_max = kwargs.pop(f'{name}max', None)
+                    limits[name] = (ax_min, ax_max)
+            for name, (ax_min, ax_max) in limits.items():
+                ax_auto = (None  # Keep autoscale state as is.
+                           if ax_min is None and ax_max is None
+                           else False)  # Turn off autoscale.
+                set_ax_lim = getattr(self, f'set_{name}lim')
+                set_ax_lim(ax_min, ax_max, emit=emit, auto=ax_auto)
         if kwargs:
             raise _api.kwarg_error("axis", kwargs)
-        return (*self.get_xlim(), *self.get_ylim())
+        lims = ()
+        for name in self._axis_names:
+            get_ax_lim = getattr(self, f'get_{name}lim')
+            lims += get_ax_lim()
+        return lims
 
     def get_legend(self):
         """Return the `.Legend` instance, or None if no legend is defined."""

lib/matplotlib/tests/test_axes.py

@@ -5641,7 +5641,7 @@ def test_shared_aspect_error():
                            "Unrecognized string 'foo' to axis; try 'on' or "
                            "'off'"),
                           (TypeError, ([1, 2], ), {},
-                           "the first argument to axis*"),
+                           "The first argument to axis*"),
                           (TypeError, tuple(), {'foo': None},
                            r"axis\(\) got an unexpected keyword argument "
                            "'foo'"),

lib/mpl_toolkits/mplot3d/tests/test_axes3d.py

@@ -213,9 +213,7 @@ def test_contour3d():
     ax.contour(X, Y, Z, zdir='z', offset=-100, cmap=cm.coolwarm)
     ax.contour(X, Y, Z, zdir='x', offset=-40, cmap=cm.coolwarm)
     ax.contour(X, Y, Z, zdir='y', offset=40, cmap=cm.coolwarm)
-    ax.set_xlim(-40, 40)
-    ax.set_ylim(-40, 40)
-    ax.set_zlim(-100, 100)
+    ax.axis(xmin=-40, xmax=40, ymin=-40, ymax=40, zmin=-100, zmax=100)
 
 
 @mpl3d_image_comparison(['contour3d_extend3d.png'], style='mpl20')