python基础（第五天）

Posted 2021-02-03 eric818

1、数据类型：

1> 可变数据类型：list, dict -----> 不可哈希

2>不可变数据类型：int, str, bool,tuple---->可哈希

哈希算法其实是一种二分查找法，效率最高。

2、字典的操作：

 1 dic = {"name": "eric", "age": 18, "sex": "male", "salary": 18000}
 2 
 3 # 增
 4 # dic["hobby"] = "basketball"
 5 # print(dic)  # {‘name‘: ‘eric‘, ‘age‘: 18, ‘sex‘: ‘male‘, ‘salary‘: 18000, ‘hobby‘: ‘basketball‘}
 6 # dic.setdefault("love", "girl")  # 如果key存在，则返回value，如果不存在，则添加
 7 # print(dic)  # {‘name‘: ‘eric‘, ‘age‘: 18, ‘sex‘: ‘male‘, ‘salary‘: 18000, ‘hobby‘: ‘basketball‘, ‘love‘: ‘girl‘}
 8 # print(dic.setdefault("age"))  # 18
 9 
10 # 删
11 # dic.pop("sex")
12 # print(dic)
13 # dic.popitem()  # 从最后一个开始删
14 # print(dic)
15 # dic.clear()
16 
17 # 改
18 dic["age"] = 28
19 print(dic)
20 
21 # 查
22 # print(dic.keys())  # dict_keys([‘name‘, ‘age‘, ‘sex‘, ‘salary‘])
23 # for i in dic.keys():
24 #     print(i)
25 
26 # for i in dic.values():
27 #     print(i)
28 
29 for k, v in dic.items():
30     print(k, v)
31 """
32 name eric
33 age 28
34 sex male
35 salary 18000
36 """

注意：字典在python3.6之前是无序，之后是有序的。