Python 学习笔记 - 7.Dictionary

Python 中的 Dictionary 和 .NET Hashtable / Dictionary 非常类似。

>>>>>> a = {1:"a", 2:"b"}  
>>>>>> a[1]  
'a'  
>>>>>> b = {'a':100, 'b':200}  
>>>>>> b[2]  
  
Traceback (most recent call last): 
  File "", line 1, in <module> 
    b[2] 
KeyError: 2  
>>>>>> b['b']  
200  
>>>>>> a[1]='aaa'  
>>>>>> a  
{1: 'aaa', 2: 'b'}  
>>>>>> del(a[1])  
>>>>>> a  
{2: 'b'}  
>>>>>> a[1]='AAAA'  
>>>>>> a  
{1: 'AAAA', 2: 'b'}  
>>>>>> a.has_key(1)  
True  
>>>>>> a.keys()  
[1, 2]  
>>>>>> a.values()  
['AAAA', 'b']  
>>>>>> a.items()  
[(1, 'AAAA'), (2, 'b')]  
>>>>>>   

 

Dictionary 的 key 是大小写敏感的。

>>>>>> b = {"a":1, "A":2}  
>>>>>> b["A"]  
2  
>>>>>> b["a"]  
1  
>>>>>>  

 

可以使用 Get() 方法避免触发 KeyError。

>>>>>> b={'a':1,'A':2}  
>>>>>> b['c']  
  
Traceback (most recent call last): 
  File "", line 1, in <module> 
    b['c'] 
KeyError: 'c'  
>>>>>> b.get('c')  
>>>>>> b.get('c','default')  
'default'  
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