Add a dedicated ColormapRegistry class

timhoffm · timhoffm · commit 664590a3ccec · 2020-09-18T01:23:05.000+02:00
diff --git a/lib/matplotlib/cm.py b/lib/matplotlib/cm.py
@@ -15,7 +15,8 @@
   normalization.
 """
 
-from collections.abc import MutableMapping
+from collections.abc import Mapping, MutableMapping
+import copy
 import functools
 
 import numpy as np
@@ -112,13 +113,44 @@ def _warn_deprecated(self):
         )
 
 
+class ColormapRegistry(Mapping):
+    r"""
+    Container for registered colormaps.
+
+    This is a read-only mapping of names to `.Colormap`\s. Use like a dict.
+
+    Returned `.Colormap`.s are copies, so that their modification does not
+    change the global definition of the colormap.
+    """
+    def __init__(self, cmaps):
+        self._cmaps = cmaps
+
+    def __getitem__(self, item):
+        try:
+            return copy.deepcopy(self._cmaps[item])
+        except KeyError:
+            raise KeyError(f"{item} is not a known colormap name")
+
+    def __iter__(self):
+        return iter(self._cmaps)
+
+    def __len__(self):
+        return len(self._cmaps)
+
+
 _cmap_registry = _gen_cmap_registry()
 locals().update(_cmap_registry)
 # This is no longer considered public API
 cmap_d = _DeprecatedCmapDictWrapper(_cmap_registry)
+colormaps = ColormapRegistry(_cmap_registry)
+r"""
+Container for all registered colormaps.
 
+This is a read-only mapping of names to `.Colormap`\s. Use like a dict.
 
-# Continue with definitions ...
+Returned `.Colormap`\s are copies, so that their modification does not
+change the global definition of the colormap.
+"""
 
 
 def register_cmap(name=None, cmap=None, data=None, lut=None):
