python字典结构化数据

https://www.cnblogs.com/evablogs/p/6692947.html

dict:

键-值(key-value)对集合{key:value},查找速度极快,但浪费内存。

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>>>  dict  =  { 'Name' 'Zara' 'Age' 7 'Class' 'First' }
>>>  dict
{ 'Age' 7 'Name' 'Zara' 'Class' 'First' }
>>>  dict .keys()                                                          #keys():以列表返回字典所有的键
[ 'Age' 'Name' 'Class' ]
>>>  dict .values()                                                        #values():以列表返回字典的所有键值
[ 7 'Zara' 'First' ]
>>>  dict .items()                                                         #items():以列表返回字典的所有键值对
[( 'Age' 7 ), ( 'Name' 'Zara' ), ( 'Class' 'First' )]
>>>  dict [ 'Class' ] = 'Second'                                               #更新键值,覆盖存在的键值,默认存取后面更新的值
>>>  dict
{ 'Age' 7 'Name' 'Zara' 'Class' 'Second' }
>>>  dict [ 'Class' ]
'Second'
>>>  dict .get( 'age' , 18 )                                                   #get('键',默认值):返回键值,如果键值不存在返回默认值不报错
18
>>>  'Name'  in  dict .keys()                                                #判断键是否存在,返回值为True/False
True
>>>  7  in  dict .values()                                                   #判断值是否存在
True
>>>  dict .clear()                                                         #清空字典中所有元素
>>>  dict
{}
>>>  del  dict                                                             #删除字典
>>>  dict
< type  'dict' >

set:无序集合,自动去重

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>>> s = set ([ 1 , 2 , 3 , 4 , 5 , 5 ])
>>> s
set ([ 1 2 3 4 5 ])                                                     #自动去除重复的值
>>> s.add( 6 )                                                             #add():新增一个元素
>>> s
set ([ 1 2 3 4 5 6 ])
>>> s.remove( 1 )                                                          #remove():移除元素
>>> s
set ([ 2 3 4 5 6 ])

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转载自www.cnblogs.com/yuer20180726/p/10790383.html