Python数据类型 — 字典
字典是python中唯一的映射类型，采用键值对（key-value）的形式存储数据。python对key进行哈希函数运算，根据计算的结果决定value的存储地址，所以字典是无序存储的，且key必须是可哈希的。可哈希表示key必须是不可变类型，如：数字、字符串、元组。
特性：无顺序、去重、查询速度快，比列表快多了、比list占用内存多
字典 = { key: value}
创建
1，使用”{}”创建：
dd = {'a': 'aaa', 'b': 'bbb'}
2，使用dict创建：
li = [('aa', 'aaa'),('bb', 'bbb')]
dd = dict(li)
print(dd)
dd = dict(aa='aaa', bb='bbb')
print(dd)
增
info["stu04"] = "Dd"
print(info)
update用于合并两个字典：字典1.update(字典2)
删
del info["stu01"]
info.popitem()
字典名.pop(‘键’)
字典名.clear()
改
dic = {"name":"jin","age":18,"sex":"male"}
dic2 = {"name":"alex","weight":75}
dic2.update(dic)
print(dic2)
dict1["stu04"]="马六"
查询、获取
print(info.get("stu07"))
print('stu02' in info)
dd = {'a': 'aaa', 'b': 'bbb', 'c': 'ccc'}
print(dd)
print('aa' in dd)
print(dd.keys())
print(dd.values())
all_items = dd.items()
print(all_items) //输出dict_items([('a', 'aaa'), ('b', 'bbb'), ('c', 'ccc')])
print(('a', 'aaa') in all_items)
print(list(all_items))
for i in all_items:
print(i)
print(list(dict1))
多级字典
travel_catlog = {
"east_China": {
"hangzhou":["西湖旅游胜地", "5A"],
"shanghai":["梦的创造地","5A"],
},
"west_China": {
"dali":["温文尔雅","3A"],
"chengdu":["天府之国","4A"]
},
"north_China": {
"beijing":["中国之最","5A"],
"tianjin":["想象之地","5A"]
},
"sourth_China":{
"hainan":["热带雨林水果之地","4A"],
"shenzheng":["科技之源","5A"]
},
}
print(travel_catlog["sourth_China"]["hainan"])
print(travel_catlog.values())
print(travel_catlog.keys())
print(travel_catlog.setdefault("sourth_China","hahahahah"))
travel_catlog.setdefault("China","hahahahah")
print(travel_catlog)
'd = {'a':'aaa','b':'bbb','c':'cccc'}
print(isinstance(d,dict))
'字典合并
a = {
's01':'Aa',
's02':'Bb',
's03':'Cc',
}
b = {
's02':'Bbbbb',
's04':'Dd',
}
a.update(b)
print(a)
'格式化生成字典
c = dict.fromkeys([1,2,3],['testd','hha','nihao'])
print(c)
字典循环、迭代
for key in a:
print(key,a[key])
for key,value in a.items():
print(key,value)
for i in dict1.keys():
print(i)
for i in dict1.values():
print(i)
字典生成式
语法：{表达式 for 迭代变量 in 可迭代对象 [if 条件表达式]}
listdemo = ['C语言中文网','c.biancheng.net']
newdict = {key:len(key) for key in listdemo}
print(newdict)
olddict={'C语言中文网': 6, 'c.biancheng.net': 15}
newdict = {v: k for k, v in olddict.items()}
print(newdict)
olddict={'C语言中文网': 6, 'c.biancheng.net': 15}
newdict = {v: k for k, v in olddict.items() if v>10}
print(newdict)
'相关知识
Python基本数据类型
老王python之基本数据类型习题
python二级选择题与分析（8）
python基础语法花多长时间
【Python】基础
Python常见的错误以及其解决方案
python机器学习
SKYNE/python
Python如何列出数组并使其成为枚举
python 花卉识别系统 用python搭建一个花卉识别系统(IT技术)
网址: Python数据类型 — 字典 https://m.huajiangbk.com/newsview484812.html
| 上一篇: 地图+游记=懒人地图:不看就OU |
下一篇: 海科路绿化景观增花添彩工程（更新 |
