Python入门3-变量2

1.字典(使用花括号定义)
  dairy_section = {}
  dairy_section["breakfast"] = ("break","milk")
  dairy_section["lunch"] = ("noodles","rices","dishes")
  dairy_section["dinner"] = ("porridge","steamed bun")
  读取时可以使用:
  1)print(dairy_section):显示全部的值
  2)dairy_section.get("breakfast"):读取特定值
  3)从字典中取键
      print_keys = dairy_section.keys()
      print_values = dairy_section.values()

2.引用序列的最后一个元素(元组和列表均属于序列)
  元组(列表)名称[-1],依次类推,比如week = ("Sunday","monday","Tuesday")
  可使用print(week[-1])打印出"Tuesday"

3.将序列分片
  1)将元组分片:例如workday = ("Monday","Tuesday","Wednesday","Thursday","Friday")
  print(workday[0:2]),显示"Monday",“Tuesday”
  2)将列表分片:例如workday = ["Mondy","Tuesday","Wednesday","Thursday","Friday"]
  print(workday[1:3]),显示"Tuesday","Wednesday"
  3)将字符分片:例如workday = "from Monday to friday"
  print(workday[2:5]),显示"om "
4.从列表中弹出元素
  today_times = [2,5,3,6]
  A = today_times.pop(0)
  print(A),显示2,且print(today_times)时显示[5,3,6]

5.计算元组、列表或字典的长度
  len(元组名或列表名或字典名)

6.处理集合
  alphabet = ['a','b','b','c','d','e','e']
  alph2 = set(alphabet)
  print(alph2)显示{'a','b','c','d','e'}

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