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python中csv模块和join函数的使用

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11/30
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在看项目的时候恰好又碰到了这两个功能，然后稍微记录一下，关于join函数，是一个经常使用的联合函数，作用就是用自己规定的字符去串联字符串和列表之类的，对于字符串来说，join函数针对的是字符串中的每一个字符元素，但是对于列表来说就是针对列表中的每一个元素，不过在字典中join只会直接串联key而不是value，所以如果要value的话要自己指定一下。 

#!/usr/bin/env python

# -*- coding:utf-8 -*-

'sep'.join(sep)  #第一个sep是自己想要使用的分隔符，第二个是自己想要操作的对象。

>>>str(sep1)

>>>"['%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s']"

>>>sep1.__str__()

>>>"['%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s']"

>>>''.join(sep1)

>>>'%s,%s,%s,%s,%s,%s,%s,%s,%s,%s,%s'

>>>''.join('%s' * 10)

>>>'%s%s%s%s%s%s%s%s%s%s'

>>>','.join('%s' * 10)

>>>'%,s,%,s,%,s,%,s,%,s,%,s,%,s,%,s,%,s,%,s'

关于csv模块，我用的比较多的是利用csv将本地文件导入到数据库当中，所以基本上都是读文件：第一种是使用reader，第二种是使用DictReader 

data = csv.reader(open(r'C:\Users\欧阳\Desktop\csv专用\test.csv', encoding='utf-8'))

rows = [row for row in data]

rows

[['\ufeff179', '阿尔布开克', 'city0000179', '', '', '', '', '', ''], ['', '安克雷奇', 'city0000180', '', '', '', '', '', ''], ['', '亚特兰大', 'city0000181', '', '', '', '', '', ''], ['', '比林斯', 'city0000182', '', '', '', '', '', ''], ['', '波士顿南', 'city0000183', '', '', '', '', '', ''], ['', '波士顿-北', 'city0000184', '', '', '', '', '', ''], ['', '芝加哥', 'city0000185', '', '', '', '', '', ''], ['', '丹佛', 'city0000186', '', '', '', '', '', ''], ['', '西雅图', 'city0000187', '', '', '', '', '', ''], ['', '莱克海瓦萨', 'city0000188', '', '', '', '', '', ''], ['', '迈阿密', 'city0000189', '', '', '', '', '', ''], ['', '休斯顿', 'city0000190', '', '', '', '', '', ''], ['', '马纳萨斯', 'city0000191', '', '', '', '', '', ''], ['', '拉斯维加斯', 'city0000192', '', '', '', '', '', ''], ['', '洛杉矶', 'city0000193', '', '', '', '', '', ''], ['', '迈阿密南部', 'city0000194', '', '', '', '', '', ''], ['', '明尼阿波利斯', 'city0000195', '', '', '', '', '', ''], ['', '纽约', 'city0000196', '', '', '', '', '', ''], ['', '奥兰多', 'city0000197', '', '', '', '', '', ''], ['', '费城', 'city0000198', '', '', '', '', '', ''], ['', '凤凰城', 'city0000199', '', '', '', '', '', ''], ['', '波特兰', 'city0000200', '', '', '', '', '', ''], ['', '盐湖城', 'city0000201', '', '', '', '', '', ''], ['', '旧金山', 'city0000202', '', '', '', '', '', ''], ['', '圣地亚哥', 'city0000203', '', '', '', '', '', ''], ['', '坦帕', 'city0000204', '', '', '', '', '', ''], ['', '卡尔加里', 'city0000205', '', '', '', '', '', ''], ['', '哈利法克斯', 'city0000206', '', '', '', '', '', ''], ['', '蒙特利尔', 'city0000207', '', '', '', '', '', ''], ['', '多伦多', 'city0000208', '', '', '', '', '', ''], ['', '温哥华', 'city0000209', '', '', '', '', '', ''], ['', '达拉斯', 'city0000210', '', '', '', '', '', ''], ['', '贝灵汉', 'city0000211', '', '', '', '', '', '']]
reader = csv.DictReader(open(r'C:\Users\欧阳\Desktop\csv专用\test.csv', encoding='utf-8'))

column = [row for row in reader]

column

[OrderedDict([('\ufeff179', ''), ('阿尔布开克', '安克雷奇'), ('city0000179', 'city0000180'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '亚特兰大'), ('city0000179', 'city0000181'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '比林斯'), ('city0000179', 'city0000182'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '波士顿南'), ('city0000179', 'city0000183'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '波士顿-北'), ('city0000179', 'city0000184'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '芝加哥'), ('city0000179', 'city0000185'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '丹佛'), ('city0000179', 'city0000186'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '西雅图'), ('city0000179', 'city0000187'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '莱克海瓦萨'), ('city0000179', 'city0000188'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '迈阿密'), ('city0000179', 'city0000189'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '休斯顿'), ('city0000179', 'city0000190'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '马纳萨斯'), ('city0000179', 'city0000191'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '拉斯维加斯'), ('city0000179', 'city0000192'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '洛杉矶'), ('city0000179', 'city0000193'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '迈阿密南部'), ('city0000179', 'city0000194'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '明尼阿波利斯'), ('city0000179', 'city0000195'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '纽约'), ('city0000179', 'city0000196'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '奥兰多'), ('city0000179', 'city0000197'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '费城'), ('city0000179', 'city0000198'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '凤凰城'), ('city0000179', 'city0000199'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '波特兰'), ('city0000179', 'city0000200'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '盐湖城'), ('city0000179', 'city0000201'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '旧金山'), ('city0000179', 'city0000202'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '圣地亚哥'), ('city0000179', 'city0000203'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '坦帕'), ('city0000179', 'city0000204'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '卡尔加里'), ('city0000179', 'city0000205'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '哈利法克斯'), ('city0000179', 'city0000206'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '蒙特利尔'), ('city0000179', 'city0000207'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '多伦多'), ('city0000179', 'city0000208'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '温哥华'), ('city0000179', 'city0000209'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '达拉斯'), ('city0000179', 'city0000210'), ('', ''), ('', ''), ('', '')]), OrderedDict([('\ufeff179', ''), ('阿尔布开克', '贝灵汉'), ('city0000179', 'city0000211'), ('', ''), ('', ''), ('', '')])]

写和读也差不多，三个步骤，显示打开文件，然后调用csv的writer方法，然后把数据写进去就可以了。 

datas = [['name', 'age'], ['Bob', 14], ['Tom', 23], ['Jerry', '']]

with open('test.csv', 'w', newline='') as f:

    writer = csv.writer(f)

    for row in datas:

        writer.writerow(row)

        #还可使用writerrows写入多行

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