python全栈闯关--5-字典

1、数据类型的划分

数据类型分为：可变数据类型，不可变数据类型

不可变数据类型：元祖、bool、int、str                    可哈希 可变数据类型：list，dic，set不可哈希

2、dic的数据结构

dic key:必须为可哈希数据类型，不可以变数据类型

      value：任意数据类型

dic 优点：二分查找，存储大量关系型数据

dic特点：3.6以前无序，3.6后有序

 

3、dic的增、删、改、查

定义

dic = {
    ‘name‘: [‘bear‘, ‘Honey‘, ‘bee‘],
    ‘myPthon‘: [{‘num1‘: 71, ‘avg_age‘: 18}
                ,{‘num1‘: 71, ‘avg_age‘: 18}
                ,{‘num1‘: 71, ‘avg_age‘: 18}],
    True: 1,
    (1, 2, 3): ‘bee‘,
    2: ‘Honey‘
}
print(dic)

The key value is an immutable type(hash),which can be tuple,bool,int,str. (immutable：不可变)

 But when the key value is a tuple, it must be an immutable type.

A varable tuple like this is not posible:(1, 2, 3, [1, 2]).

It will reopot errors:TypeError: unhashable type: ‘list‘.

增

dic1 = {‘age‘: 18, ‘name‘: ‘bear‘, ‘sex‘: ‘male‘}
dic2 = {}
# if the key value does not exist to be added to the dictionary
dic1[‘high‘] = 185
# if the dictionary has a key value, update the corresponding value to the dictionary (corresponding:相符的)
dic1[‘age‘] = 15

# Key value does not exist, default add none to dictionary
dic1.setdefault(‘weight‘)
# The key value does note exist, if the second parameter is specified,add the (key,value) pair to the dictionary
dic1.setdefault(‘weight‘, 90)
# If the key value already exists,the specified value will not be update to the dictionary
dic1.setdefault(‘name‘, ‘bee‘)

删 改 查

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