Merge pull request #7 from enbritely/frozenordereddict

Implement FrozenOrderedDict

frozendict/__init__.py

@@ -2,6 +2,7 @@ import collections
 import operator
 import functools
 
+
 class frozendict(collections.Mapping):
 
     def __init__(self, *args, **kwargs):
@@ -29,3 +30,36 @@ class frozendict(collections.Mapping):
             self.__hash = functools.reduce(operator.xor, hashes, 0)
 
         return self.__hash
+
+
+class FrozenOrderedDict(collections.Mapping):
+    """
+    It is an immutable wrapper around ordered dictionaries that implements the complete :py:class:`collections.Mapping`
+    interface. It can be used as a drop-in replacement for dictionaries where immutability and ordering are desired.
+    """
+
+    def __init__(self, *args, **kwargs):
+        self.__dict = collections.OrderedDict(*args, **kwargs)
+        self.__hash = None
+
+    def __getitem__(self, key):
+        return self.__dict[key]
+
+    def copy(self, **add_or_replace):
+        return FrozenOrderedDict(self, **add_or_replace)
+
+    def __iter__(self):
+        return iter(self.__dict)
+
+    def __len__(self):
+        return len(self.__dict)
+
+    def __repr__(self):
+        return '<FrozenOrderedDict %s>' % repr(self.__dict)
+
+    def __hash__(self):
+        if self.__hash is None:
+            hashes = map(hash, self.items())
+            self.__hash = functools.reduce(operator.xor, hashes, 0)
+
+        return self.__hash