Python 字典dict使用介绍

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