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','linuxeye.com'])) >>> fdict {'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 "Tue Oct 15 21:54:26 CST 2013", line 1, in NameError: name 'product_dict' is not defined
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