Implement simple print method for single node element

01_binary_search_trees/bst.py

@@ -83,7 +83,7 @@ class BinarySearchTree():
         Prints a nice version of the binary search node
         """
         #TODO
-        return "aaa"
+        return self.root_node.__str__()
 
     @staticmethod
     def is_search_tree(a_tree_root):
@@ -129,3 +129,9 @@ class BinarySearchNode():
 
     def has_right_child(self):
         return self.right_child is not None
+
+    def __str__(self):
+        """
+        prints a single tree node.
+        """
+        return (str(self.left_child.value) + " " +  str(self.value) + " " + str(self.right_child.value) )

01_binary_search_trees/bst_test.py

@@ -200,7 +200,13 @@ class test_binary_search_tree(unittest.TestCase):
         node_val4 = 16
         bst.add(node_val4)
 
-        self.assertEqual(bst.__str__(), "aaa")
+        #    6
+        #   / \
+        #  4   10
+        #       \
+        #        16
+
+        self.assertEqual(bst.__str__(), "4 6 10")
 
 if __name__ == '__main__':
     unittest.main()