diff --git a/src/__pycache__/pretty_print.cpython-39.pyc b/src/__pycache__/pretty_print.cpython-39.pyc
new file mode 100644
index 0000000..8d1da4a
Binary files /dev/null and b/src/__pycache__/pretty_print.cpython-39.pyc differ
diff --git a/src/__pycache__/tree.cpython-39.pyc b/src/__pycache__/tree.cpython-39.pyc
index 2aa560a..1294641 100644
Binary files a/src/__pycache__/tree.cpython-39.pyc and b/src/__pycache__/tree.cpython-39.pyc differ
diff --git a/src/pretty_print.py b/src/pretty_print.py
new file mode 100644
index 0000000..778708d
--- /dev/null
+++ b/src/pretty_print.py
@@ -0,0 +1,5 @@
+import json
+
+def pp(json_obj, indent=2):
+  dumps = json.dumps(json_obj, indent=2)
+  print(dumps)
diff --git a/src/tree.py b/src/tree.py
index 33f49a0..51bde54 100644
--- a/src/tree.py
+++ b/src/tree.py
@@ -119,6 +119,41 @@ class NerdTree():
 
     return d
 
+  def compute_aggregate_recursively(self, node=None):
+    '''
+      node is the rootnode of the subtree
+      at the moment compute size and number of items of subtree starting from node
+    '''
+
+    subtree = {
+        'subtree_size' : 0,
+        'subtree_items' : 0,
+        }
+
+    node = node or self.json_tree
+
+    for item in node.get('children') or []:
+
+      if item['type'] == 'd':
+        if item.get('subtree_size') is None:
+          subtree_compute = self.compute_aggregate_recursively(item)
+        else:
+          subtree_compute = {
+              'subtree_size' : item['subtree_size'],
+              'subtree_items' : item['subtree_items'],
+              }
+        ## if you want count the current directory as item you must sum 1
+        ## if you want count the current directory size you must include item['size']
+        subtree['subtree_size'] += subtree_compute['subtree_size'] + item['size']
+        subtree['subtree_items'] += subtree_compute['subtree_items'] + 1 
+      else:
+        subtree['subtree_size'] += item['size']
+        subtree['subtree_items'] += 1
+
+    # return subtree
+    node.update(subtree)
+    return subtree
+
   def tree_from_struct(self, rootnode, prec_seps=[]):
     '''
     recursively produce a string for representing the tree