常用数据类型操作（四）

元组

• 概念：有序的 不可变的 元素集合
• 定义

  1. 一个元素
     t = (888,)
     print(type(t), t)
  
  2. 多个元素
     # 一般写法
     t = ("coder", [6, 8], 5)
     print(type(t), t)
  
     # 不建议使用
     t = 3, 6, 8, "xiaoxiong"
     print(type(t), t)
  
     # 內建函数，将一个列表转换为元组
     l = [3, 6, 8, 10]
     change_tuple = tuple(l)
     print(type(change_tuple), change_tuple)
  
     # 元组嵌套
     t = (6, 8, ("w", "x"))
     print(type(t), t)
  
  3. 元组推导式
     nums = (1, 2, 3, 4, 5, 6)
     num_tuple = (num * 2 for num in nums if num >= 5)
     print(type(num_tuple), num_tuple)
  

• 操作
  • 查

    1. 获取单个元素：索引
       t = (1, 2, 3, 4, 5)
       print(t[1])
       print(t[-1])
    
    2. 获取多个元素：切片
       t = (1, 3, 5, 7, 9)
       print(t[0:2])
       print(t[::-1])
    

  • 获取
    • 获取指定元素个数

      """
      count(item)
      """
      t = (1, 2, 3, 2, 2)
      c = t.count(2)
      print(c)
      c = t.count(2)
      print(c)
      

    • 获取指定元素索引

      t = (1, 2, 3, 2, 2)
      idx = t.index(2, 2)
      print(idx)
      

    • 获取元素个数

      t = (1, 2, 3, 2, 2)
      length = len(t)
      print(length)
      

    • 获取元素最小值

      t = (1, 2, 3, 2, 2)
      min_num = min(t)
      print(min_num)
      

    • 获取元素最大值

      t = (1, 2, 3, 2, 2)
      max_num = max(t)
      print(max_num)
      

  • 判定

    1. 元素 in 元组
    2. 元素 not in 元组
    t = (3, 5, 7, 9, 1)
    print(23 in t)
    print(7 in t)
    

  • 比较
    • cmp

      """
      Python2.x：针对每个元素，从左到右逐一比较
      tuple1 < tuple2：-1
      tuple1 == tuple2：0
      tuple1 > tuple2：1
      """
      result = cmp((1, 2, 3), (2, 3, 4))
      result = cmp((1, 3, 5), [1, 2, 3])
      print(result)
      

    • 运算符

      """
      Python3.x：针对每个元素，从左到右逐一比较
      """
      <
      ==
      >
      result = (1, 2, 3) < (3, 5, 7)
      print(result)
      

  • 拼接
    • 乘法运算

      num_tuple = (3, 5, 7)
      print(num_tuple * 3)
      

    • 加法运算

      """
      注意：只能元组类型和元组类型相加
      """
      t_one = (1, 3, 5)
      t_two = (2, 4, 6)
      print(t_one + t_two)
      

  • 拆包

    a = 66
    b = 88
    b, a = (a, b)
    print(a, b)