ENH: add method to un-register a color map

tacaswell · tacaswell · commit f2f5ca24f8fc · 2019-08-26T09:07:17.000-04:00
diff --git a/doc/users/next_whats_new/2019-08_tac.rst b/doc/users/next_whats_new/2019-08_tac.rst
@@ -0,0 +1,6 @@
+
+Add ``cm.unregister_cmap`` function
+-----------------------------------
+
+`.cm.unregister_cmap` allows users to remove a color map that they
+have previously registered.
diff --git a/lib/matplotlib/cm.py b/lib/matplotlib/cm.py
@@ -144,6 +144,28 @@ def get_cmap(name=None, lut=None):
         return cmap_d[name]._resample(lut)
 
 
+def unregister_cmap(name):
+    """
+    Remove a colormap recognized by :func:`get_cmap`.
+
+    You may not remove built in color maps.
+
+    If the named color map is not registered, returns with no error, raises
+    if you try to de-register a default color map.
+
+    Raises
+    ------
+    ValueError
+       If you
+    """
+    if name not in cmap_d:
+        return
+    if name in globals():
+        raise ValueError(f"Can not unregister {name} which is a builtin "
+                         "color map.")
+    cmap_d.pop(name)
+
+
 class ScalarMappable:
     """
     This is a mixin class to support scalar data to RGBA mapping.
diff --git a/lib/matplotlib/tests/test_cm.py b/lib/matplotlib/tests/test_cm.py
@@ -13,3 +13,15 @@ def test_register_cmap():
 
     with pytest.warns(UserWarning):
         mcm.register_cmap('viridis'[::-1], mcm.get_cmap('viridis'))
+
+
+    mcm.unregister_cmap('viridis'[::-1])
+    with pytest.raises(ValueError):
+        mcm.get_cmap('viridis'[::-1])
+    # test that second time is error free
+    mcm.unregister_cmap('viridis'[::-1])
+
+
+def test_unregister_cmap():
+    with pytest.raises(ValueError):
+        mcm.unregister_cmap('viridis')
