010-python基础-数据类型-字典

Posted 2020-08-19

字典一种key - value 的数据类型，key是唯一的。

字典是无序的，默认。

 

一、创建

1 info = {
2     ‘stu1101‘: "TengLan Wu",
3     ‘stu1102‘: "LongZe Luola",
4     ‘stu1103‘: "XiaoZe Maliya",
5 }

 二、增加

1 >>> info["stu1104"] = "苍井空"
2 >>> info
3 {‘stu1102‘: ‘LongZe Luola‘, ‘stu1104‘: ‘苍井空‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1101‘: ‘TengLan Wu‘}

三、修改

1 >>> info[‘stu1101‘] = "武藤兰"
2 >>> info
3 {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1101‘: ‘武藤兰‘}

 

四、删除

 1 >>> info
 2 {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1101‘: ‘武藤兰‘}
 3 >>> info.pop("stu1101") #标准删除姿势
 4 ‘武藤兰‘
 5 >>> info
 6 {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘}
 7 >>> del info[‘stu1103‘] #换个姿势删除
 8 >>> info
 9 {‘stu1102‘: ‘LongZe Luola‘}
10 >>> 
11 >>> 
12 >>> 
13 >>> info = {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘}
14 >>> info
15 {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘} #随机删除
16 >>> info.popitem()
17 (‘stu1102‘, ‘LongZe Luola‘)
18 >>> info
19 {‘stu1103‘: ‘XiaoZe Maliya‘}

五、查找

 1 >>> info = {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘}
 2 >>> 
 3 >>> "stu1102" in info #标准用法
 4 True
 5 >>> info.get("stu1102")  #获取
 6 ‘LongZe Luola‘
 7 >>> info["stu1102"] #同上，但是看下面
 8 ‘LongZe Luola‘
 9 >>> info["stu1105"]  #如果一个key不存在，就报错，get不会，不存在只返回None
10 Traceback (most recent call last):
11   File "<stdin>", line 1, in <module>
12 KeyError: ‘stu1105‘

六、多级字典嵌套及操作（略）

七、循环字典

1 #方法1
2 for key in info:
3     print(key,info[key])
4 #方法2
5 for k,v in info.items():  # 会先把dict转成list,数据里大时莫用
6     print(k,v)

 

八、其他

 1 #values
 2 >>> info.values()
 3 dict_values([‘LongZe Luola‘, ‘XiaoZe Maliya‘])
 4 #keys    ##相对常用
 5 >>> info.keys()
 6 dict_keys([‘stu1102‘, ‘stu1103‘])
 7 #setdefault
 8 >>> info.setdefault("stu1106","Alex")
 9 ‘Alex‘
10 >>> info
11 {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1106‘: ‘Alex‘}
12 >>> info.setdefault("stu1102","龙泽萝拉")
13 ‘LongZe Luola‘
14 >>> info
15 {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1106‘: ‘Alex‘}
16 #update 
17 >>> info
18 {‘stu1102‘: ‘LongZe Luola‘, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1106‘: ‘Alex‘}
19 >>> b = {1:2,3:4, "stu1102":"龙泽萝拉"}
20 >>> info.update(b)
21 >>> info
22 {‘stu1102‘: ‘龙泽萝拉‘, 1: 2, 3: 4, ‘stu1103‘: ‘XiaoZe Maliya‘, ‘stu1106‘: ‘Alex‘}
23 #items
24 info.items()
25 dict_items([(‘stu1102‘, ‘龙泽萝拉‘), (1, 2), (3, 4), (‘stu1103‘, ‘XiaoZe Maliya‘), (‘stu1106‘, ‘Alex‘)])
26 #通过一个列表生成默认dict,有个没办法解释的坑，少用吧这个
27 >>> dict.fromkeys([1,2,3],‘testd‘)
28 {1: ‘testd‘, 2: ‘testd‘, 3: ‘testd‘}