diff --git a/lib/mpl_toolkits/axisartist/axislines.py b/lib/mpl_toolkits/axisartist/axislines.py
index 6f28e5c61a2f..1d695c129ae2 100644
--- a/lib/mpl_toolkits/axisartist/axislines.py
+++ b/lib/mpl_toolkits/axisartist/axislines.py
@@ -354,9 +354,7 @@ def get_gridlines(self, which="major", axis="both"):
                 locs.extend(self.axes.xaxis.major.locator())
             if which in ("both", "minor"):
                 locs.extend(self.axes.xaxis.minor.locator())
-
-            for x in locs:
-                gridlines.append([[x, x], [y1, y2]])
+            gridlines.extend([[x, x], [y1, y2]] for x in locs)
 
         if axis in ("both", "y"):
             x1, x2 = self.axes.get_xlim()
@@ -365,9 +363,7 @@ def get_gridlines(self, which="major", axis="both"):
                 locs.extend(self.axes.yaxis.major.locator())
             if self.axes.yaxis._minor_tick_kw["gridOn"]:
                 locs.extend(self.axes.yaxis.minor.locator())
-
-            for y in locs:
-                gridlines.append([[x1, x2], [y, y]])
+            gridlines.extend([[x1, x2], [y, y]] for y in locs)
 
         return gridlines
 
diff --git a/lib/mpl_toolkits/axisartist/grid_finder.py b/lib/mpl_toolkits/axisartist/grid_finder.py
index ff61887f9ef2..4e963be6f5be 100644
--- a/lib/mpl_toolkits/axisartist/grid_finder.py
+++ b/lib/mpl_toolkits/axisartist/grid_finder.py
@@ -34,7 +34,7 @@ def _find_line_box_crossings(xys, bbox):
         umin, vmin = bbox.min[sl]
         umax, vmax = bbox.max[sl]
         for u0, inside in [(umin, us > umin), (umax, us < umax)]:
-            crossings.append([])
+            cross = []
             idxs, = (inside[:-1] ^ inside[1:]).nonzero()
             for idx in idxs:
                 v = vs[idx] + (u0 - us[idx]) * dvs[idx] / dus[idx]
@@ -42,7 +42,8 @@ def _find_line_box_crossings(xys, bbox):
                     continue
                 crossing = (u0, v)[sl]
                 theta = np.degrees(np.arctan2(*dxys[idx][::-1]))
-                crossings[-1].append((crossing, theta))
+                cross.append((crossing, theta))
+            crossings.append(cross)
     return crossings