Remove DefaultMapping abstract base class.

cachetools/cache.py

@@ -1,7 +1,10 @@
-from .abc import DefaultMapping
+from collections.abc import MutableMapping
 
 
 class _DefaultSize(object):
+
+    __slots__ = ()
+
     def __getitem__(self, _):
         return 1
 
@@ -12,9 +15,11 @@ def pop(self, _):
         return 1
 
 
-class Cache(DefaultMapping):
+class Cache(MutableMapping):
     """Mutable mapping to serve as a simple cache or cache base class."""
 
+    __marker = object()
+
     __size = _DefaultSize()
 
     def __init__(self, maxsize, getsizeof=None):
@@ -73,6 +78,29 @@ def __iter__(self):
     def __len__(self):
         return len(self.__data)
 
+    def get(self, key, default=None):
+        if key in self:
+            return self[key]
+        else:
+            return default
+
+    def pop(self, key, default=__marker):
+        if key in self:
+            value = self[key]
+            del self[key]
+        elif default is self.__marker:
+            raise KeyError(key)
+        else:
+            value = default
+        return value
+
+    def setdefault(self, key, default=None):
+        if key in self:
+            value = self[key]
+        else:
+            self[key] = value = default
+        return value
+
     @property
     def maxsize(self):
         """The maximum size of the cache."""