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 "<stdin>", line 1, in <module>
NameError: name 'product_dict' is not defined