Good Tree
1
2
3
[< 3 >]
Bad Tree
1
2
2
[< 2 >, < 3 >]

#!/usr/bin/python
class NodeBad:
  def __init__(self, value, c=[]):
    self.value = value
    self.children = c
  def addchild(self, node):
    self.children.append(node)
  def __str__(self):
    return '< %s >' % self.value
  def __repr__(self):
    return '< %s >' % self.value


class NodeGood:
  def __init__(self, value):
    self.value = value
    self.children = []
  def addchild(self, node):
    self.children.append(node)
  def __str__(self):
    return '< %s >' % self.value
  def __repr__(self):
    return '< %s >' % self.value

if __name__ == '__main__':
  print 'Good Tree'
  ng = NodeGood(1) # Root Node
  rootgood = ng
  ng.addchild(NodeGood(2)) # 1nd Child
  ng = ng.children[0]
  ng.addchild(NodeGood(3)) # 2nd Child

  print rootgood.value
  print rootgood.children[0].value
  print rootgood.children[0].children[0].value
  print rootgood.children[0].children

  print 'Bad Tree'
  nb = NodeBad(1) # Root Node
  rootbad = nb
  nb.addchild(NodeBad(2)) # 1st Child
  nb = nb.children[0]
  nb.addchild(NodeBad(3)) # 2nd Child

  print rootbad.value
  print rootbad.children[0].value
  print rootbad.children[0].children[0].value
  print rootbad.children[0].children

def __init__(self, value, c=None):

if c == None:
  c = []