>a=['apple','banana','pear','orange']
> a
['apple', 'banana', 'pear', 'orange']
> a={1:'apple',2:'banana',3:'pear',4:'orange'}
> a
{1: 'apple', 2: 'banana', 3: 'pear', 4: 'orange'}
> a[2]
'banana'
> a[5]
Traceback (most recent call last):
 File "<pyshell#31>", line 1, in <module>
 a[5]
KeyError: 5
> a[6]='grap'
> a
{1: 'apple', 2: 'banana', 3: 'pear', 4: 'orange', 6: 'grap'}

> a

{1: 'apple', 2:'banana', 3: 'pear', 4: 'orange', 6: 'grap'}

>a.items()

dict_items([(1,'apple'), (2, 'banana'), (3, 'pear'), (4, 'orange'), (6, 'grap')])

>a.update({1:10,2:20})

> a

{1: 10, 2: 20,3: 'pear', 4: 'orange', 6: 'grap'}

#{1:10,2:20}替换了{1: 'apple', 2: 'banana'}