Python字典的创建

方法一：

>>> blank_dict = {}
>>> product_dict = {\'MAC\':8000,\'Iphone\':5000, \'ipad\':4000, \'mp3\': 300}
>>> product_dict
{\'ipad\': 4000, \'MAC\': 8000, \'Iphone\': 5000, \'mp3\': 300}
>>> blank_dict,product_dict
({}, {\'ipad\': 4000, \'MAC\': 8000, \'Iphone\': 5000, \'mp3\': 300})

方法二：
从Python 2.2版本开始

>>> fdict = dict(([\'www\',\'www.linuxeye.com\'],[\'blog\',\'blog.linuxeye.com\']))
>>> fdict
{\'blog\': \'blog.linuxeye.com\', \'www\': \'www.linuxeye.com\'}

方法三：
从Python 2.3版本开始, 可以用一个很方便的内建方法fromkeys() 来创建一个”默认”字典, 字典中元素具有相同的值 (如果没有给出， 默认为None):

>>> fk_dict = {}.fromkeys((\'a\',\'b\'),\'LinuxEye\')
>>> fk_dict
{\'a\': \'LinuxEye\', \'b\': \'LinuxEye\'}
>>> fk2_dict = {}.fromkeys((\'yeho\',\'python\'))
>>> fk2_dict
{\'python\': None, \'yeho\': None}
>>> fk3_dict = {}.fromkeys(\'yeho\',\'python\')
>>> fk3_dict
{\'y\': \'python\', \'h\': \'python\', \'e\': \'python\', \'o\': \'python\'}

Python字典查、增、删、改

>>> product_dict = {\'MAC\':8000,\'Iphone\':5000, \'mp3\': 300}
>>> product_dict[\'Iphone\']
5000
>>> product_dict[\'ipad\'] = 4000 #增
>>> product_dict
{\'ipad\': 4000, \'MAC\': 8000, \'Iphone\': 5000, \'mp3\': 300}
 
>>> product_dict.keys() #查看索引
[\'ipad\', \'MAC\', \'Iphone\', \'mp3\']
>>> product_dict.values() #查看值
[4000, 8000, 5000, 300]
>>> product_dict.items()
[(\'ipad\', 4000), (\'MAC\', 8000), (\'Iphone\', 5000), (\'mp3\', 300)]
>>> for product,price in product_dict.items():
...  print product,price
...
ipad 4000
MAC 8000
Iphone 5000
mp3 300
>>> product_dict.has_key(\'Iphone\') #判断key是否存在
True
>>> product_dict.has_key(\'Itouch\')
False
 
>>> product_dict.pop(\'MAC\') #删除指定key和value
 8000
 >>> product_dict
 {\'ipad\': 4000, \'Iphone\': 5000, \'mp3\': 300}
 >>> product_dict.popitem() #删除第一个key和value
 (\'ipad\', 4000)
 >>> product_dict
 {\'Iphone\': 5000, \'mp3\': 300}
 
 >>> product_dict = {\'Iphone\': 5000, \'mp3\': 300}
 >>> del product_dict[\'Iphone\'] #用del函数删除指定key和value
 >>> product_dict
 {\'mp3\': 300}
 >>> product_dict[\'mp3\'] = 299 #改
 >>> product_dict
 {\'mp3\': 299}
 >>> product_dict.clear() #清空字典内容（空字典）
 >>> product_dict
 {}
 >>> del product_dict #删除字典
 >>> product_dict = {\'mp3\': 300}
 >>> del product_dict #已删除报错
 Traceback (most recent call last):
  File \"\", line 1, in 
 NameError: name \'product_dict\' is not defined