DOC: Add note about locators at top of ticker docs

dopplershift · dopplershift · commit 04979348a6cc · 2020-11-26T14:20:14.000-07:00
The note about not sharing `Locator` instances should be more prominent
than hiding in the base class docs, which most users have no need to
examine.
diff --git a/lib/matplotlib/ticker.py b/lib/matplotlib/ticker.py
@@ -81,6 +81,19 @@
 
 The default minor locator is `NullLocator`, i.e., no minor ticks on by default.
 
+.. note::
+    `Locator` instances should not be used with more than one
+    `~matplotlib.axis.Axis` or `~matplotlib.axes.Axes`. So instead of::
+
+        locator = matplotlib.ticker.MultipleLocator(5)
+        ax.xaxis.set_major_locator(locator)
+        ax2.xaxis.set_major_locator(locator)
+
+    do the following instead::
+
+        ax.xaxis.set_major_locator(matplotlib.ticker.MultipleLocator(5))
+        ax2.xaxis.set_major_locator(matplotlib.ticker.MultipleLocator(5))
+
 Tick formatting
 ---------------
 
