Require a match between fixed ticks and ticklabels.

efiring · efiring · commit dbe6f358d347 · 2020-05-04T11:02:07.000-10:00
diff --git a/lib/matplotlib/axis.py b/lib/matplotlib/axis.py
@@ -1635,6 +1635,11 @@ def set_ticklabels(self, ticklabels, *, minor=False, **kwargs):
         locator = (self.get_minor_locator() if minor
                    else self.get_major_locator())
         if isinstance(locator, mticker.FixedLocator):
+            if len(locator.locs) != len(ticklabels):
+                raise ValueError(
+                    "The number of FixedLocator locations"
+                    f" ({len(locator.locs)}) does not match"
+                    f" the number of ticklabels ({len(ticklabels)}).")
             tickd = {loc: lab for loc, lab in zip(locator.locs, ticklabels)}
             func = functools.partial(self._format_with_dict, tickd)
             formatter = mticker.FuncFormatter(func)
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -4441,8 +4441,8 @@ def test_set_get_ticklabels():
     # set ticklabel to 1 plot in normal way
     ax[0].set_xticks(range(10))
     ax[0].set_yticks(range(10))
-    ax[0].set_xticklabels(['a', 'b', 'c', 'd'])
-    ax[0].set_yticklabels(['11', '12', '13', '14'])
+    ax[0].set_xticklabels(['a', 'b', 'c', 'd'] + 6 * [''])
+    ax[0].set_yticklabels(['11', '12', '13', '14'] + 6 * [''])
 
     # set ticklabel to the other plot, expect the 2 plots have same label
     # setting pass get_ticklabels return value as ticklabels argument
@@ -4464,6 +4464,14 @@ def test_subsampled_ticklabels():
     assert labels == ['b', 'd', 'f', 'h', 'j']
 
 
+def test_mismatched_ticklabels():
+    fig, ax = plt.subplots()
+    ax.plot(np.arange(10))
+    ax.xaxis.set_ticks([1.5, 2.5])
+    with pytest.raises(ValueError):
+        ax.xaxis.set_ticklabels(['a', 'b', 'c'])
+
+
 @image_comparison(['retain_tick_visibility.png'])
 def test_retain_tick_visibility():
     fig, ax = plt.subplots()
