Python tree

tree.py

def tree(root):
  """
  Node(label = "string", children = [list of Node])
  """
  ret = [root.label]
  ln = len(root.children)
  for i, child in enumerate(root.children):
    for j, s in enumerate(tree(child)):
      char = '│ '
      if i == ln - 1:  # last child
        if j == 0:  # first line of last child
          char = '└─'
        else:
          char = '  '
      elif j == 0:  # first line of other children
        char = '├─'
      ret.append('%s %s' % (char, s))
  return ret