python--字典和集合

字典

字典一种key - value 的数据类型

语法：

info={
     ‘01‘:‘Tom‘,
     ‘02‘:‘Jim‘,
     ‘03‘:‘Lucy‘,
     ‘04‘:‘Lily‘
 }

字典的特性：

• dict是无序的
• key必须是唯一的,所以自动去重

 增加：

In [20]: info[‘05‘]=‘Hans‘

In [21]: print(info)
{‘02‘: ‘Jim‘, ‘03‘: ‘Lucy‘, ‘01‘: ‘Tom‘, ‘04‘: ‘Lily‘, ‘05‘: ‘Hans‘}

 修改：

In [22]: info[‘03‘]=‘LiGang‘

In [23]: print(info)
{‘02‘: ‘Jim‘, ‘03‘: ‘LiGang‘, ‘01‘: ‘Tom‘, ‘04‘: ‘Lily‘, ‘05‘: ‘Hans‘}

 删除：

删除有两种方法：

dict.pop(key)  #第一种方法 

In [24]: info.pop(‘01‘)
Out[24]: ‘Tom‘

In [25]: print(info)
{‘02‘: ‘Jim‘, ‘03‘: ‘LiGang‘, ‘04‘: ‘Lily‘, ‘05‘: ‘Hans‘}

del dict[key]  #第二种方法

In [26]: del info[‘05‘]

In [27]: print(info)
{‘02‘: ‘Jim‘, ‘03‘: ‘LiGang‘, ‘04‘: ‘Lily‘}

还有一种是随机删除

dict.popitem()  #随机删除字典里的key和value

In [29]: info.popitem()
Out[29]: (‘03‘, ‘LiGang‘)

In [30]: info.popitem()
Out[30]: (‘04‘, ‘Lily‘)

In [31]: info.popitem()
---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-31-203673e70575> in <module>()
----> 1 info.popitem()

KeyError: ‘popitem(): dictionary is empty‘

In [32]: print(info)
{}

 查找：

In [35]: info
Out[35]: {‘01‘: ‘Tom‘, ‘02‘: ‘Jim‘, ‘03‘: ‘Lucy‘, ‘04‘: ‘Lily‘}
In [34]: ‘01‘ in info   #标准用法
Out[34]: True

In [36]: info.get(‘01‘)  #获取
Out[36]: ‘Tom‘

多级字典嵌套及操作：