class Trunk(object):
  '''樹(shù)干'''
  def __str__(self):
    pass

  def subtree(self):
    pass

class Composite(Trunk):
  def __init__(self, left=None, right=None, length=None):
    self.left=left
    self.right=right
    self.length=length

  def __str__(self):
    # 這個(gè)結(jié)果是在調(diào)用subtree()的時(shí)候返回
    if self.length:
      return "(" + self.left.__str__() + ", " + self.right.__str__() + ")" + ": " + str(self.length) 
    else:
      return "(" + self.left.__str__() + ", " + self.right.__str__() + ")"

    # 這里其實(shí)就是一個(gè)技巧，通過(guò)這個(gè)函數(shù)返回下一級(jí)的對(duì)象，也就是它既是對(duì)象還可以是對(duì)象的容器
    def subtree(self):        
      return Composite(self.left, self.right)

class Leaf(Trunk):
  '''葉子類(lèi)，它沒(méi)辦法繼續(xù)延伸了'''
  def __init__(self, name, length=None):
    self.name = name
    self.length=length
    self.left = None
    self.right = None

  def __str__(self):
    return self.name + ": " + str(self.length)

  def subtree(self):
    return Leaf(self.name, self.length)


if __name__ == "__main__":
  # 只有葉子那么就直接返回__str__的拼裝結(jié)果
  t1 = Leaf('A', 0.71399)
  print t1
  # 有個(gè)2個(gè)葉子的組合，返回的是2個(gè)葉子的對(duì)象的組合
  t2 = Composite(Leaf('B', -0.00804), 
    Leaf('C', 0.07470))
  print t2
  # 這個(gè)是嵌套的葉子的組合，樹(shù)干上面有樹(shù)枝，樹(shù)枝上面有葉子
  t3 = Composite(Leaf('A', 0.71399),
    Composite(Leaf('B', -0.00804), 
        Leaf('C', 0.07470), 0.1533), 0.0666)

  print t3
  # 直接通過(guò)左右節(jié)點(diǎn)找到對(duì)應(yīng)的葉子對(duì)象了
  t4 = t3.right.right.subtree()
  print t4
  # t3的左樹(shù)其實(shí)就是葉子對(duì)象了
  t5 = t3.left.subtree()
  print t5

class BaseHandler:
  # 它起到了鏈的作用
  def successor(self, successor):
    self.successor = successor

class ScoreHandler1(BaseHandler):
  def handle(self, request):
    if request > 90 and request <= 100:
      return "A+"
    else:
      # 否則傳給下一個(gè)鏈，下同，但是我是要return回結(jié)果的
      return self.successor.handle(request)

class ScoreHandler2(BaseHandler):
  def handle(self, request):
    if request > 80 and request <= 90:
      return "A"
    else:
      return self.successor.handle(request)

class ScoreHandler3(BaseHandler):
  def handle(self, request):
    if request > 70 and request <= 80:
      return "B+"
    else:
      return "unsatisfactory result"

class Client:
  def __init__(self):
    h1 = ScoreHandler1()
    h2 = ScoreHandler2()
    h3 = ScoreHandler3()
    # 注意這個(gè)順序，h3包含一個(gè)類(lèi)似于default結(jié)果的東西，是要放在最后的，其他的順序是無(wú)所謂的，比如h1和h2
    h1.successor(h2)
    h2.successor(h3)

    requests = {'zhangsan': 78,
          'lisi': 98,
          'wangwu': 82,
          'zhaoliu': 60}
    for name, score in requests.iteritems():
      print '{} is {}'.format(name, h1.handle(score))

if __name__== "__main__":
  client = Client()