Merge branch 'fix_cachedict'

py/util/cachedict.py

@@ -3,20 +3,39 @@
 """
 
 class CacheDict(dict):
-    def __init__(self, n):
+    """
+    A dictionary that keeps only the last n items added
+    """
+    def __init__(self, n, d=None):
+        """
+        Create CacheDict with n keys cached.
+
+        If d is a dict, use that to initialize the key/value pairs
+        """
         self._keys = [None,]*n
         self._current = -1
         self._n = n
+
+        if type(d) == dict:
+            for key, value in d.items():
+                self[key] = value
+
+    #- Needed by pickle to reconstruct the object.
+    #- Pickle tries to reconstruct the dictionary via __setitem__ before
+    #- filling in _keys, _current, _n.  This allows it to create a new
+    #- object first to get those right, before calling __setitem__
+    def __reduce__(self):
+        return type(self), (self._n, dict(self))
 
     def __setitem__(self, key, value):
+        """Sets the key/value, possibly dropping an earlier cached key/value"""
         if key in self:
             return
-            
+
         i = self._current = (self._current + 1) % self._n
         if self._keys[i] is not None:
             del self[self._keys[i]]
 
         self._keys[i] = key
         dict.__setitem__(self, key, value)
 
-