diff --git a/Tree.py b/Tree.py
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--- /dev/null
+++ b/Tree.py
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+#!/usr/bin/python
+# -*- coding: utf-8 -*-
+# \file Tree.py
+# \brief TODO
+# \author Florent Guiotte <florent.guiotte@gmail.com>
+# \version 0.1
+# \date 21 sept. 2017
+#
+# TODO details
+
+import collections
+
+def Tree():
+    return collections.defaultdict(Tree)
+
+def walk(node):
+    """iterate tree in pre-order depth"""
+    if isinstance(node, str): yield "+-" + node
+    if not isinstance(node, str):
+        for child in node.values():
+            for n in walk(child):
+                yield "| " + n
+
+if __name__ == "__main__":
+    t = Tree()
+    t[1] = "test"
+    t[2][1] = "yoyo"
+    t[2][2] = "qweqweqwe"
+    t[3][1] = "u wot"
+    t[2][3][1] = "yoloy"
+    t[2][3][2][1] = "qwe"
+    t[4] = "wat"
+
+    for i in walk(t):
+        print(i)