Tweak axis_direction demo.

- Show the curvilinear grid, without which the orientation of the ticks
  on the surrounding rectangular frame doesn't make much sense.
- Constrained layout works reasonably well enough, no need to set axes
  spacings by hand, but this exposed a bug where GridlinesCollection set
  paths to None (instead of an empty list), which breaks get_datalim
  (which calls len(paths)).
- Inline most intermediate constructs in setup_axes (avoiding lines like
  `extreme_finder=extreme_finder`).
- Many small style fixes.

Author: anntzer

galleries/examples/axisartist/demo_axis_direction.py

@@ -18,74 +18,52 @@
 
 def setup_axes(fig, rect):
     """Polar projection, but in a rectangular box."""
-
     # see demo_curvelinear_grid.py for details
-    tr = Affine2D().scale(np.pi/180., 1.) + PolarAxes.PolarTransform()
-
-    extreme_finder = angle_helper.ExtremeFinderCycle(20, 20,
-                                                     lon_cycle=360,
-                                                     lat_cycle=None,
-                                                     lon_minmax=None,
-                                                     lat_minmax=(0, np.inf),
-                                                     )
-
-    grid_locator1 = angle_helper.LocatorDMS(12)
-    grid_locator2 = grid_finder.MaxNLocator(5)
-
-    tick_formatter1 = angle_helper.FormatterDMS()
-
-    grid_helper = GridHelperCurveLinear(tr,
-                                        extreme_finder=extreme_finder,
-                                        grid_locator1=grid_locator1,
-                                        grid_locator2=grid_locator2,
-                                        tick_formatter1=tick_formatter1
-                                        )
-
-    ax1 = fig.add_subplot(
-        rect, axes_class=axisartist.Axes, grid_helper=grid_helper)
-    ax1.axis[:].toggle(ticklabels=False)
-
-    ax1.set_aspect(1.)
-    ax1.set_xlim(-5, 12)
-    ax1.set_ylim(-5, 10)
-
-    return ax1
-
-
-def add_floating_axis1(ax1):
-    ax1.axis["lat"] = axis = ax1.new_floating_axis(0, 30)
+    grid_helper = GridHelperCurveLinear(
+        Affine2D().scale(np.pi/180., 1.) + PolarAxes.PolarTransform(),
+        extreme_finder=angle_helper.ExtremeFinderCycle(
+            20, 20,
+            lon_cycle=360, lat_cycle=None,
+            lon_minmax=None, lat_minmax=(0, np.inf),
+        ),
+        grid_locator1=angle_helper.LocatorDMS(12),
+        grid_locator2=grid_finder.MaxNLocator(5),
+        tick_formatter1=angle_helper.FormatterDMS(),
+    )
+    ax = fig.add_subplot(
+        rect, axes_class=axisartist.Axes, grid_helper=grid_helper,
+        aspect=1, xlim=(-5, 12), ylim=(-5, 10))
+    ax.axis[:].toggle(ticklabels=False)
+    ax.grid(color=".9")
+    return ax
+
+
+def add_floating_axis1(ax):
+    ax.axis["lat"] = axis = ax.new_floating_axis(0, 30)
     axis.label.set_text(r"$\theta = 30^{\circ}$")
     axis.label.set_visible(True)
-
     return axis
 
 
-def add_floating_axis2(ax1):
-    ax1.axis["lon"] = axis = ax1.new_floating_axis(1, 6)
+def add_floating_axis2(ax):
+    ax.axis["lon"] = axis = ax.new_floating_axis(1, 6)
     axis.label.set_text(r"$r = 6$")
     axis.label.set_visible(True)
-
     return axis
 
 
-fig = plt.figure(figsize=(8, 4))
-fig.subplots_adjust(left=0.01, right=0.99, bottom=0.01, top=0.99,
-                    wspace=0.01, hspace=0.01)
+fig = plt.figure(figsize=(8, 4), layout="constrained")
 
 for i, d in enumerate(["bottom", "left", "top", "right"]):
-    ax1 = setup_axes(fig, rect=241++i)
-    axis = add_floating_axis1(ax1)
+    ax = setup_axes(fig, rect=241+i)
+    axis = add_floating_axis1(ax)
     axis.set_axis_direction(d)
-    ax1.annotate(d, (0, 1), (5, -5),
-                 xycoords="axes fraction", textcoords="offset points",
-                 va="top", ha="left")
+    ax.set(title=d)
 
 for i, d in enumerate(["bottom", "left", "top", "right"]):
-    ax1 = setup_axes(fig, rect=245++i)
-    axis = add_floating_axis2(ax1)
+    ax = setup_axes(fig, rect=245+i)
+    axis = add_floating_axis2(ax)
     axis.set_axis_direction(d)
-    ax1.annotate(d, (0, 1), (5, -5),
-                 xycoords="axes fraction", textcoords="offset points",
-                 va="top", ha="left")
+    ax.set(title=d)
 
 plt.show()

lib/mpl_toolkits/axisartist/axislines.py

@@ -432,7 +432,7 @@ def clear(self):
 
         # Init gridlines before clear() as clear() calls grid().
         self.gridlines = gridlines = GridlinesCollection(
-            None, transform=self.transData,
+            [], transform=self.transData,
             colors=mpl.rcParams['grid.color'],
             linestyles=mpl.rcParams['grid.linestyle'],
             linewidths=mpl.rcParams['grid.linewidth'])