Python Learning Notes _6_ dictionary common operations

Dictionary operations

A dictionary is a set of "key-value pairs" enclosed by a pair of curly braces, and each key-value pair is an element of the dictionary, and the elements are unordered in the dictionary, with the following common actions:

info = {

' Name ': ' Xiaoming ',

' Sex ': ' Nan ',

' Age ': 20,

' ID ': 1,

}

Print (info[' id ') # value via key

Print (info[' addr ') # value via key

Print (Info.get (' id ')) # value via key

Print (Info.get (' addr ')) # value via key

#用中括号取值和get方法取值的区别, the Get method does not get the key when

#不会报错, the value of the brackets can not find the key will be an error, so the Get method is more common

#get方法还可以多传一个参数, if get is not key, then return this parameter value.

#如果不写的话, the default get is not returned to none

info[' addr '] = ' Beijing ' #给字典新增一个键值对

Info.setdefault (' phone ', 13811111) #给字典新增一个键值对

info[' id '] = 7

#在有这个key的情况下那就是修改这个key的value

#没有这个key的话, is the new

#字典是无序的

del info[' addr '] #删除字典的一个指定元素 (key-value pairs)

Info.pop (' addr ') #删除字典的一个指定元素 (key-value pairs),

#pop删除的时候必须得指定key, the Pop method returns the value corresponding to the deleted key

Info.popitem () #随机删除一个元素

Info.clear () #清空字典

Example:

all = {

' Car ':

{

' Color ': [' red ', ' yellow ', ' black '],

' Moeny ': 1111111,

' Pailiang ': ' 2.5L ',

' Name ': "BMW"

} ,

' Car1 ':

{

' Color ': [' red ', ' yellow ', ' black '],

' Moeny ': 1111111,

' Pailiang ': ' 2.5L ',

' Country ': "China"

},

' Car2 ':

{

' Color ': [' red ', ' yellow ', ' black '],

' Moeny ': 1111111,

' Pailiang ': ' 2.5L '

}

}

Print (All)

All.get (' car '). Get (' color ') [1] = ' Orange ' # change car color to orange

Print (All)

all[' car ' [' Color '][1]= ' Blue ' # change the color of car to blue

Print (All)

Print (All.keys ()) #获取该字典的所有key (the outermost dictionary, if nested inside the dictionary, regardless)

Print (All.values ()) #获取该字典所有的value

Print (All.items ()) #获取字典的key和value, used when looping

#直接循环字典循环的是字典的key, if you want to get the key and value in the loop

#那么就要用 the. Items () method

Python Learning Notes _6_ dictionary common operations