Implemented Memento design pattern.

pypatterns/structural/memento.py

@@ -0,0 +1,41 @@
+from copy import deepcopy
+
+
+class Memento(object):
+    """
+    Memento class as part of the Memento design pattern.
+    """
+    def __init__(self, state):
+        """
+        Initialize a new Memento instance.
+
+        @param state: The state to save in this Memento.
+        @type state: dict
+        """
+        self.__state = state
+
+    @property
+    def state(self):
+        return self.__state
+
+
+class Originator(object):
+    """
+    Originator base class as part of the Memento design pattern.
+    """
+    def commit(self):
+        """
+        Commit this objects state to a memento.
+
+        @return: A memento instance with this objects state.
+        """
+        return Memento(deepcopy(self.__dict__))
+
+    def rollback(self, memento):
+        """
+        Rollback this objects state to a previous state.
+
+        @param memento: The memento object holding the state to rollback to.
+        @type memento: Memento
+        """
+        self.__dict__ = memento.state