Store the number along with the todo item.

The number represents the position in the backing store, and can be
printed on the stdout to help the user to identify the correct task.

Todo.py

@@ -14,8 +14,8 @@ class Todo(TodoBase.TodoBase):
     base class, mainly by interpreting the start and due dates of task.
     """
 
-    def __init__(self, p_str):
-        TodoBase.TodoBase.__init__(self, p_str)
+    def __init__(self, p_str, p_number=-1):
+        TodoBase.TodoBase.__init__(self, p_str, p_number)
 
     def get_date(self, p_tag):
         """ Given a date tag, return a date object. """

TodoBase.py

@@ -19,9 +19,10 @@ class TodoBase(object):
     in a todo item.
     """
 
-    def __init__(self, p_src):
+    def __init__(self, p_src, p_number=-1):
         self.src = ""
         self.fields = {}
+        self.number = p_number
 
         self.set_text(p_src)
 

TodoList.py

@@ -45,7 +45,8 @@ class TodoList(object):
         """
 
         if re.search(r'\S', p_src):
-            todo = Todo.Todo(p_src)
+            number = len(self._todos) + 1
+            todo = Todo.Todo(p_src, number)
             self._todos.append(todo)
 
     def delete(self, p_number):