字典的实用.md

字典

defaultdict

当字典中的key不存在时，返回不再是keyError，而是一个默认值，这个默认值是int, list，set, str等。也就是返回一个空值。

类型	返回值
int	0
str	‘’
list	[]

字典用函数作为值

items = {
		'laptop': lambda x: x * 600, 
  	'raspberry pi': lambda x: x * 5,
		'arduino': lambda x: x * 50
	}

quantity = 4
value of laptop = items['laptop'](quantity)
print(f'value of {quantity} laptops = ${value_of_laptop}')

有哪些好用的库

字典库easydict和addict

pip install easydict
pip install addict

基本使用

>>> from addict import Dict
>>> mapping = Dict()
>>> mapping.a.b.c.d.e = 2
>>> mapping
{'a': {'b': {'c': {'d': {'e': 2}}}}}

针对json

>>> from easydict import EasyDict as edict
>>> from simplejson import loads
>>> j = """{
"Buffer": 12,
"List1": [
    {"type" : "point", "coordinates" : [100.1,54.9] },
    {"type" : "point", "coordinates" : [109.4,65.1] },
    {"type" : "point", "coordinates" : [115.2,80.2] },
    {"type" : "point", "coordinates" : [150.9,97.8] }
]
}"""
>>> d = edict(loads(j))
>>> d.Buffer
12
>>> d.List1[0].coordinates[1]
54.9

优先推荐使用 addict

treelib