python数据类型之字典（一）

时间：2023-02-07 13:02:32
>>> dInfo = dict(Wangdachui=3000,Niuyun=2000,Linling=4500,Tianqi=8000)

>>> dInfo

{'Wangdachui': 3000, 'Niuyun': 2000, 'Linling': 4500, 'Tianqi': 8000}

字典定义：

字典是一种映射类型，是由key（键）和value（值）组成的键值对，key是不可变类型，可以是数字、字符串、元组等等

创建字典：

1、直接创建：

ainfo = {'Wangdachui':3000,'Niuyun':2000.'Linling':4500,'Tianqi':8000}

2、间接创建：

>>> info = [('Wangdachui',3000),('Niuyun',2000),('Linling',4500),('Tianqi',8000)]

>>> binfo = dict(info)

>>> binfo

{'Wangdachui': 3000, 'Niuyun': 2000, 'Linling': 4500, 'Tianqi': 8000}

>>> info = [['Wangdachui',3000],['Niuyun',2000],['Linling',4500],['Tianqi',8000]]

>>> dict(info)

{'Wangdachui': 3000, 'Niuyun': 2000, 'Linling': 4500, 'Tianqi': 8000}
>>> dInfo = dict(Wangdachui=3000,Niuyun=2000,Linling=4500,Tianqi=8000)

>>> dInfo

{'Wangdachui': 3000, 'Niuyun': 2000, 'Linling': 4500, 'Tianqi': 8000}
>>> info = (('Wangdachui',3000),('Niuyun',2000),('Linling',4500),('Tianqi',8000))

>>> dict(info)

{'Wangdachui': 3000, 'Niuyun': 2000, 'Linling': 4500, 'Tianqi': 8000}
>>> info = (['Wangdachui',3000],['Niuyun',2000],['Linling',4500],['Tianqi',8000])

>>> dict(info)

{'Wangdachui': 3000, 'Niuyun': 2000, 'Linling': 4500, 'Tianqi': 8000}

上面五种方法，有四种其实是列表+元组的排列组合。。

如何将value设为默认值？

>>> aDict = {}.fromkeys(('Wangdachui','Niuyun','Linling','Tianqi'),3000)

>>> aDict

{'Wangdachui': 3000, 'Niuyun': 3000, 'Linling': 3000, 'Tianqi': 3000}

注意这里fromkeys的第一个元素必须是不可变的元组，不能是可变的列表

如何将两个列表组合成一个字典？　　

>>> names = ['Wangdachui','Niuyun','Linling','Tianqi']

>>> salaries = [3000,2000,4500,8000]

>>> dict(zip(names,salaries))

{'Wangdachui': 3000, 'Niuyun': 2000, 'Linling': 4500, 'Tianqi': 8000}

创建字典案例：

给出一个列表的数据，包括公司代码，公司名称和股票价格

>>> plist = [('AXP', 'American Express Company', '86.40'),

                     ('BA', 'The Boeing Company', '122.64'),

                     ('CAT', 'Caterpillar Inc.', '99.44'),

                     ('CSCO', 'Cisco Systems,Inc.', '23.78'),

                     ('CVX', 'Chevron Corporation', '115.91')]

如何构造公司代码和股票价格的字典

{'AXP': '86.40', 'BA': '122.64', 'CAT': '99.44', 'CSCO': '23.78', 'CVX': '115.91'}

这里有两种方法：

1、用for循环

>>> plist

[('AXP', 'American Express Company', '86.40'), ('BA', 'The Boeing Company', '122.64'), ('CAT', 'Caterpillar Inc.', '99.44'), ('CSCO', 'Cisco Systems,Inc.', '23.78'), ('CVX', 'Chevron Corporation', '115.91')]

>>> alist =[]

>>> blist =[]

>>> for i in range(5):

    aStr = plist[i][0]

    bStr = plist[i][2]

    alist.append(aStr)

    blist.append(bStr)

>>> aDict = dict(zip(alist,blist))

>>> aDict

{'AXP': '86.40', 'BA': '122.64', 'CAT': '99.44', 'CSCO': '23.78', 'CVX': '115.91'}

2、用生成键值对的方式

>>> plist

[('AXP', 'American Express Company', '86.40'), ('BA', 'The Boeing Company', '122.64'), ('CAT', 'Caterpillar Inc.', '99.44'), ('CSCO', 'Cisco Systems,Inc.', '23.78'), ('CVX', 'Chevron Corporation', '115.91')]

>>> aDict ={}

>>> for data in plist:

    aDict[data[0]] = data[2]

>>> aDict

{'AXP': '86.40', 'BA': '122.64', 'CAT': '99.44', 'CSCO': '23.78', 'CVX': '115.91'}

相关文章