使用python从csv文件中仅获取所需的行

Question

如何使用python从csv文件中获取每个第3行？

import csv

with open ('data.csv','r') as infile:
    contents = csv.reader(infile, delimiter =' ')
then???

csv文件如下所示：

aaaaaaaaaaaaaaaa
bbbbbbbbbbbbbbbb
only recquired line
cccccccccccccccccccccccccc
ddddddddddddddddddddddddd
only recquired line

结果如下：

only recquired line
only recquired line

Answer 1

为避免将整个文件加载到内存中，您可以使用itertools.islice

from itertools import islice
with open ('data.csv','r') as infile:
    x = islice(infile, 2, None, 3)
    for line in x:
            print line

Answer 2

for index, line in enumerate(fileOfInterest, 1):
   if index % 3 == 0:
       doSomething

或者，您可以使用python的extended slice表示法，如下所示：

for line in fileOfInterest[2::3]
   doSomething

然而，1_CR的回答是我要去的那个！

Answer 3

with open('test.csv') as hf:
    print [line for line in list(hf)[2::3]]

Answer 4

使用extended slice notation：

for i in contents.splitlines(True)[2::3]:
    print (i)