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