python【数据类型：字典】

字典的定义

infos = {'name':'张晓红','sex':'女','address':'上海','age':18}

 stus = {"name":"张三","sex":"女"}
 print(list(stus.values()))      #结果输出：['女', '张三']
 print(list(stus.keys()))        #结果输出：['sex', 'name']
 print(list(stus.items()))       #结果输出：[('sex', '女'), ('name', '张三')]

字典实现账号注册

 stus = {"name":"张三"}
 stus.update({"sex": "男"})
 print(stus)         #结果输出：{'name': '张三', 'sex': '男'}
 stus.update({"sex":"女"})
 print(stus)         #结果输出：{'name': '张三', 'sex': '女'}

 d = {'a':68,'w':62,'c':91,'d':83,'e':93,'f':89,'g':67}
 print(list(d.items()))      #结果输出：[('w', 62), ('a', 68), ('f', 89), ('c', 91), ('g', 67), ('d', 83), ('e', 93)]
 d2 = sorted(d.items(),key=lambda x:x[1])    #lambda x:x[1] 根据字典的value排序，lambda x:x[0] 根据字典的key排序
 print(d2)               #结果输出：[('w', 62), ('g', 67), ('a', 68), ('d', 83), ('f', 89), ('c', 91), ('e', 93)]
 print(d2[:2])           #结果输出：[('w', 62), ('g', 67)]

 d3 = sorted(d.items(),key=lambda x:x[1],reverse=True)
 print(d3)               #结果输出：[('e', 93), ('c', 91), ('f', 89), ('d', 83), ('a', 68), ('g', 67), ('w', 62)]
 print(d3[:2])           #结果输出：[('e', 93), ('c', 91)]