python 读写csv

对于大多数的CSV格式的数据读写问题,都可以使用csv库。例如,假设你在一个名叫stock.csv文件中

有一些股票市场数据：
[root@node01 python]# python t5.py 
['AA', '39.48', '6/11/2007', '9:36am', '-0.18', '181800']
['AIG', '71.38', '6/11/2007', '9:36am', '-0.15', '195500']
['AXP', '62.58', '6/11/2007', '9:36am', '-0.46', '935000']
['BA', '98.31', '6/11/2007', '9:36am', '+0.12', '104800']
['C', '53.08', '6/11/2007', '9:36am', '-0.25', '360900']
['CAT', '78.29', '6/11/2007', '9:36am', '-0.23', '225400']
[root@node01 python]# vim t5.py

[root@node01 python]# python t5.py 
['AA', '39.48', '6/11/2007', '9:36am', '-0.18', '181800']
<type 'list'>
['AIG', '71.38', '6/11/2007', '9:36am', '-0.15', '195500']
<type 'list'>
['AXP', '62.58', '6/11/2007', '9:36am', '-0.46', '935000']
<type 'list'>
['BA', '98.31', '6/11/2007', '9:36am', '+0.12', '104800']
<type 'list'>
['C', '53.08', '6/11/2007', '9:36am', '-0.25', '360900']
<type 'list'>
['CAT', '78.29', '6/11/2007', '9:36am', '-0.23', '225400']
<type 'list'>



[root@node01 python]# cat t5.py 
import csv
with open('stocks.csv') as f:
   f_csv = csv.reader(f)
   headers = next(f_csv)
   for row in f_csv:
     print row
     print type(row)


在上面的代码中,row是一个列表,因此为了访问某个字段,你需要使用下标。

如row[0] 访问Symbol,row[4]访问Change.

由于这种下标访问通常会引起混淆,你可以考虑使用命名元组,例如:


另外一个选择就是讲数据读取到一个字典序列中去,可以这样做:

[root@node01 python]# cat t6.py 
import csv
with open('stocks.csv') as f:
 f_csv = csv.DictReader(f)
 for row in f_csv:
   print row
   print type(row)

[root@node01 python]# python t6.py 
{'Symbol': 'AA', 'Volume': '181800', 'Time': '9:36am', 'Date': '6/11/2007', 'Price': '39.48', 'Change': '-0.18'}
<type 'dict'>
{'Symbol': 'AIG', 'Volume': '195500', 'Time': '9:36am', 'Date': '6/11/2007', 'Price': '71.38', 'Change': '-0.15'}
<type 'dict'>
{'Symbol': 'AXP', 'Volume': '935000', 'Time': '9:36am', 'Date': '6/11/2007', 'Price': '62.58', 'Change': '-0.46'}
<type 'dict'>
{'Symbol': 'BA', 'Volume': '104800', 'Time': '9:36am', 'Date': '6/11/2007', 'Price': '98.31', 'Change': '+0.12'}
<type 'dict'>
{'Symbol': 'C', 'Volume': '360900', 'Time': '9:36am', 'Date': '6/11/2007', 'Price': '53.08', 'Change': '-0.25'}
<type 'dict'>
{'Symbol': 'CAT', 'Volume': '225400', 'Time': '9:36am', 'Date': '6/11/2007', 'Price': '78.29', 'Change': '-0.23'}
<type 'dict'>



为了写入CSV数据,你仍然可以使用csv模块,不过这时候创建一个writer对象

[root@node01 python]# cat t7.py 
import csv
headers = ['Symbol','Price','Date','Time','Change','Volume']
rows = [('AA', 39.48, '6/11/2007', '9:36am', -0.18, 181800),
('AIG', 71.38, '6/11/2007', '9:36am', -0.15, 195500),
('AXP', 62.58, '6/11/2007', '9:36am', -0.46, 935000),
]
with open('aaa.csv','w') as f:
    f_csv = csv.writer(f)
    f_csv.writerow(headers)
    f_csv.writerows(rows)