Nicolas Dumazet

class Node(object):
  ...
  def children_count(self):
    """
    Returns the number of children

    @param node node to get nb of children
    @returns number of children: 0, 1, 2
    """
    cnt = 0
    if self.left:
      cnt += 1
    if self.right:
      cnt += 1
    return cnt

  def delete(self, data):
    node, parent = self.lookup(data)
    if node is None:
      return
    children_count = node.children_count()
    if children_count == 0:
      # if node has no children, just remove it
      if parent.left is node:
        parent.left = None
      else:
        parent.right = None
    elif children_count == 1:
  ...