>>> a_list = [[1,2,3],[4,5],[6,7]]
>>> a_list[1][1]
5
>>> a_dict = {1:{"name":"qiwsir"},2:"python","email":"qiwsir@gmail.com"}
>>> a_dict
{1: {'name': 'qiwsir'}, 2: 'python', 'email': 'qiwsir@gmail.com'}
>>> a_dict[1]['name']  #一个嵌套的dict访问其值的方法：一层一层地写出键
'qiwsir'

>>> website = {1:"google","second":"baidu",3:"facebook","twitter":4}

>>>#用d.keys()的方法得到dict的所有键，结果是list
>>> website.keys()
[1, 'second', 3, 'twitter']

>>>#用d.values()的方法得到dict的所有值，如果里面没有嵌套别的dict，结果是list
>>> website.values()
['google', 'baidu', 'facebook', 4]

>>>#用items()的方法得到了一组一组的键值对，
>>>#结果是list，只不过list里面的元素是元组
>>> website.items()
[(1, 'google'), ('second', 'baidu'), (3, 'facebook'), ('twitter', 4)]

>>> for key in website.keys():
...   print key,type(key)
... 
1 <type 'int'>
second <type 'str'>
3 <type 'int'>
twitter <type 'str'>

>>>#下面的方法和上面的方法是一样的
>>> for key in website:
...   print key,type(key)
... 
1 <type 'int'>
second <type 'str'>
3 <type 'int'>
twitter <type 'str'>

>>> for value in website.values():
...   print value
... 
google
baidu
facebook
4

>>> for key in website:
...   print website[key]
... 
google
baidu
facebook
4

>>> for k,v in website.items():
...   print str(k)+":"+str(v)
... 
1:google
second:baidu
3:facebook
twitter:4

>>> for k in website:
...   print str(k)+":"+str(website[k])
... 
1:google
second:baidu
3:facebook
twitter:4

>>> website
{1: 'google', 'second': 'baidu', 3: 'facebook', 'twitter': 4}
>>> website.get(1)   
'google'
>>> website.get("second")
'baidu'

>>> len(website)
4
>>> website
{1: 'google', 'second': 'baidu', 3: 'facebook', 'twitter': 4}

>>> new_web = website.copy()  #拷贝一份，这个拷贝也叫做浅拷贝，对应着还有深拷贝。
>>> new_web　          #两者区别，可以google一下。
{1: 'google', 'second': 'baidu', 3: 'facebook', 'twitter': 4}

>>>#d.pop(key)，根据key删除相应的键值对，并返回该值
>>> new_web.pop('second')
'baidu'

>>> del new_web[3]　  #没有返回值，如果删除键不存在，返回错误
>>> new_web
{1: 'google', 'twitter': 4}
>>> del new_web[9]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
KeyError: 9

>>> cnweb
{'qq': 'first in cn', 'python': 'qiwsir.github.io', 'alibaba': 'Business'}
>>> website
{1: 'google', 'second': 'baidu', 3: 'facebook', 'twitter': 4}

>>> website.update(cnweb)  #把cnweb合并到website内
>>> website　        #变化了
{'qq': 'first in cn', 1: 'google', 'second': 'baidu', 3: 'facebook', 'python': 'qiwsir.github.io', 'twitter': 4, 'alibaba': 'Business'}
>>> cnweb　         #not changed
{'qq': 'first in cn', 'python': 'qiwsir.github.io', 'alibaba': 'Business'}