added __len__

Project 5/Stack.py

@@ -21,7 +21,7 @@ class Stack[T]:
        
         ''' initializes an empty stack '''
         self._data = LinkedList()
-        
+
     def __len__(self) -> int:
         ''' allows the len function to be called using an ArrayStack object, e.g.,
                stack = ArrayStack()
@@ -29,7 +29,7 @@ class Stack[T]:
         Returns:
             number of elements in the stack, as an integer
         '''
-        pass
+        return len(self._data)
 
     def push(self, item: T) -> None: 
         ''' pushes a given item of arbitrary type onto the stack