Python。文本fi中的偶数行

Question

所以，我需要一个代码从txt文件中读取偶数行。 这是一个任务的例子。

输入：

Bravely bold Sir Robin rode forth from Camelot
Yes, brave Sir Robin turned about
He was not afraid to die, O brave Sir Robin
And gallantly he chickened out
He was not at all afraid to be killed in nasty ways
Bravely talking to his feet
Brave, brave, brave, brave Sir Robin
He beat a very brave retreat

输出：

Yes, brave Sir Robin turned about
And gallantly he chickened out
Bravely talking to his feet
He beat a very brave retreat

Answer 1

使用itertools.islice：

import itertools
import sys

with open('input.txt') as f:
    sys.stdout.writelines(itertools.islice(f, 1, None, 2))

Answer 2

像这样的：

with open('in.txt','r') as f:
    file = f.readlines()

for i in range(1,8,2):
    print file[i]

它将打印：

Yes, brave Sir Robin turned about

And gallantly he chickened out

Bravely talking to his feet

He beat a very brave retreat

Answer 3

所以，只输出偶数行。

i = 1
f = open('file')
for line in f.readlines():
    if i % 2 == 0 :
        print line
    i += 1