Another update from ingydotnet^djgoku

Task/Tree-traversal/Python/tree-traversal-2.py

@@ -0,0 +1,61 @@
+from collections import namedtuple
+from sys import stdout
+
+class Node(namedtuple('Node', 'data, left, right')):
+    __slots__ = ()
+
+    def preorder(self, visitor):
+        if self is not None:
+            visitor(self.data)
+            Node.preorder(self.left, visitor)
+            Node.preorder(self.right, visitor)
+
+    def inorder(self, visitor):
+        if self is not None:
+            Node.inorder(self.left, visitor)
+            visitor(self.data)
+            Node.inorder(self.right, visitor)
+
+    def postorder(self, visitor):
+        if self is not None:
+            Node.postorder(self.left, visitor)
+            Node.postorder(self.right, visitor)
+            visitor(self.data)
+
+    def levelorder(self, visitor, more=None):
+        if self is not None:
+            if more is None:
+                more = []
+            more += [self.left, self.right]
+            visitor(self.data)
+        if more:
+            Node.levelorder(more[0], visitor, more[1:])
+
+
+def printwithspace(i):
+    stdout.write("%i " % i)
+
+
+tree = Node(1,
+            Node(2,
+                 Node(4,
+                      Node(7, None, None),
+                      None),
+                 Node(5, None, None)),
+            Node(3,
+                 Node(6,
+                      Node(8, None, None),
+                      Node(9, None, None)),
+                 None))
+
+
+if __name__ == '__main__':
+    stdout.write('  preorder: ')
+    tree.preorder(printwithspace)
+    stdout.write('\n   inorder: ')
+    tree.inorder(printwithspace)
+    stdout.write('\n postorder: ')
+    tree.postorder(printwithspace)
+    stdout.write('\nlevelorder: ')
+    tree.levelorder(printwithspace)
+    stdout.write('\n')