Fix #23: Refactor LFUCache.

CHANGES.rst

@@ -1,13 +1,14 @@
 0.7.0 UNRELEASED
 ----------------
 
-- Add `choice` argument to ``RRCache`` constructor.
-
 - Deprecate ``TTLCache.ExpiredError``.
 
-- Refactor ``LRUCache``, ``TTLCache``.
+- Add `choice` argument to ``RRCache`` constructor.
+
+- Refactor ``LFUCache``, ``LRUCache`` and ``TTLCache``.
 
-- Use custom ``NullContext`` implementation.
+- Always use custom ``NullContext`` implementation for unsynchronized
+  function decorators.
 
 
 0.6.0 2014-10-13

cachetools/lfucache.py

@@ -2,6 +2,7 @@
 from .decorators import cachedfunc
 from .lock import RLock
 
+import collections
 import operator
 
 
@@ -14,28 +15,29 @@ class LFUCache(Cache):
     """
 
     def __init__(self, maxsize, getsizeof=None):
-        if getsizeof is None:
-            Cache.__init__(self, maxsize)
-        else:
-            Cache.__init__(self, maxsize, lambda e: getsizeof(e[0]))
-            self.getsizeof = getsizeof
+        Cache.__init__(self, maxsize, getsizeof=getsizeof)
+        self.__counter = collections.Counter()
 
     def __getitem__(self, key, cache_getitem=Cache.__getitem__):
-        entry = cache_getitem(self, key)
-        entry[1] += 1
-        return entry[0]
+        value = cache_getitem(self, key)
+        self.__counter[key] += 1
+        return value
 
     def __setitem__(self, key, value, cache_setitem=Cache.__setitem__):
-        cache_setitem(self, key, [value, 0])
+        cache_setitem(self, key, value)
+        self.__counter[key] += 1
+
+    def __delitem__(self, key, cache_delitem=Cache.__delitem__):
+        cache_delitem(self, key)
+        del self.__counter[key]
 
     def popitem(self):
         """Remove and return the `(key, value)` pair least frequently used."""
-        items = ((key, Cache.__getitem__(self, key)[1]) for key in self)
         try:
-            key, _ = min(items, key=operator.itemgetter(1))
+            key, _ = min(self.__counter.items(), key=operator.itemgetter(1))
         except ValueError:
             raise KeyError('cache is empty')
-        return (key, self.pop(key))
+        return key, self.pop(key)
 
 
 def lfu_cache(maxsize=128, typed=False, getsizeof=None, lock=RLock):