ENH: adding suggested names to ColormapRegistry missing key error

lib/matplotlib/cm.py

@@ -15,6 +15,7 @@
 """
 
 from collections.abc import Mapping
+import difflib
 import functools
 
 import numpy as np
@@ -88,7 +89,12 @@
         try:
             return self._cmaps[item].copy()
         except KeyError:
-            raise KeyError(f"{item!r} is not a known colormap name") from None
+            known = list(self._cmaps)
+            if len(best := difflib.get_close_matches(item, known, cutoff=.1)):
+                msg = f"Did you mean one of {best}?"
+            else:
+                msg = ""
+            raise KeyError(f"{item!r} is not a known colormap name. {msg}") from None
 
     def __iter__(self):
         return iter(self._cmaps)

lib/matplotlib/tests/test_colors.py

@@ -1697,3 +1697,14 @@ def test_to_rgba_array_none_color_with_alpha_param():
     assert_array_equal(
         to_rgba_array(c, alpha), [[0., 0., 1., 1.], [0., 0., 0., 0.]]
     )
+
+
+def test_close_error_name():
+    with pytest.raises(KeyError) as exinfo:
+        matplotlib.colormaps["grays"]
+
+    msg = exinfo.value.args[0]
+
+    assert "Grays" in msg
+    assert "gray" in msg
+    assert "gray_r" in msg