栈和队列

• 内置的数据结构

  {} key-value 通过key找value很快

  [] 序列 通过index取值非常块

  () 元组

  {1，}集合

  'eytd'字符串

• 不是python内置的

  • Queue队列：先进先出FIFO

    '''
    先进先出
    Queue（）创建一个空的新队列
    '''
    class Queue():
        def __init__(self):
            self.items = []
        def enqueue(self, item):
            self.items.insert(0, item)
        def dequeue(self):
            return self.items.pop()
        def isEmpty(self):
            return self.items == []
        def size(self):
            return len(self.items)
        
    q = Queue()
    q.enqueue(1)
    q.enqueue(2)
    q.enqueue(3)
    print(q.dequeue())
    print(q.dequeue())
    print(q.dequeue())
    

  • Stack栈：后进先出LIFO

    '''
    栈顶、栈尾、先进后出
    Stack()创建一个空的新栈，它不需要参数，并返回一个空栈
    peek()从栈返回栈顶，但不会删除它，不需要参数，不修改栈
    isEmpty()测试栈是否为空
    '''
    
    class Stack:
        def __init__(self):
            self.items = []
        def push(self,item):
            self.items.append(item)
        def pop(self):
            return self.items.pop()
        def peek(self):
            return len(self.items)-1
        def isEmpty(self):
            return self.items == []
        def size(self):
            return len(self.items)
    
    stack = Stack()
    stack.push(1)
    stack.push(2)
    stack.push(3)
    print("栈顶元素下标：", stack.peek())
    print(stack.isEmpty())
    print("元素个数：", stack.size())
    print(stack.pop())
    print(stack.pop())
    print(stack.pop())
    

• 结合继承

  # 方法一
  class Foo:
      def __init__(self):
          self.items = []
      def put(self,item):
          self.items.append(item)
      def get(self):
          return self.items.pop()
  #队列
  class Queue(Foo):
      def get(self):
          return self.items.pop(0)
  #栈
  class Stack(Foo):pass
  
  #方法二
  class Foo:
      def __init__(self):
          self.items = []
      def put(self,item):
          self.items.append(item)
      def get(self):
          return self.items.pop() if self.index else self.items.pop(0)
  #队列
  class Queue(Foo):
      def __init__(self):
          self.index = 0
          Foo.__init__(self)
  #栈
  class Stack(Foo):
      def __init__(self):
          self.index = 1
          Foo.__init__(self)
          
          
  q = Queue()
  q.put(1)
  q.put(2)
  print(q.get())
  print(q.get())
  
  stack = Stack()
  stack.put(3)
  stack.put(4)
  print(stack.get())
  print(stack.get())
  

• 练习

  #创建Mypickle类
  import pickle
  # 栈
  class Stack:
      def __init__(self):
          self.items = []
      def put(self,item):
          self.items.append(item)
      def get(self):
          return self.items.pop()
  
  class Mypickle:
      def __init__(self, path):
          self.file = path
      def dump(self,obj):
          with open(self.file, 'ab') as f:
              pickle.dump(obj, f)
      def load(self):
          with open(self.file, 'rb') as f:
              while True:
                  try:
                      yield pickle.load(f)
                  except EOFError:
                      break
      # def load(self):
      #     l = []
      #     with open(self.file, 'rb') as f:
      #         while True:
      #             try:
      #                 l.append(pickle.load(f))
      #             except EOFError:
      #                 break
      #     return l
  pic = Mypickle('pickcle_file')
  # s1 = Stack()
  # s1.put('111')
  # s1.put('222')
  # s1.put('333')
  # pic.dump(s1)
  # s2 = Stack()
  # s2.put('aaa')
  # s2.put('bbb')
  # s2.put('ccc')
  # pic.dump(s2)
  for i in pic.load():
      print(i.items)
      #['111', '222', '333']
      #['aaa', 'bbb', 'ccc']